To all:
The deadline for Part 1 of the project is over.
Some of you have sent your files in 07 format. Do give me some time to access as currently my laptop cant open them. need to use another computer to open that.
So dont worry about that.
Some of you have not followed my instructions. No acknowledgments, incorrect length of reflection. Some just copied wholesale from the website without understanding fully wat was being written. Some just took from the textbook which was really short. Marks would be deducted accordingly if so.
Late submissions from now onwards will result in loss of marks except for those who have approached me personally due to valid reasons. No submissions will cause a ZERO MARK to be awarded.
Note: some of your pics arent uploaded in the blog. But pls make use of them when you get together in your groups to design the poster. Thanks
A gentle reminder: This project will be counted as a CA mark in Term 3. No submission or late submission will result in YOU getting 0 marks in Term 3. TAKE NOTE!
Friday, June 20, 2008
Refraction of Light by 2E2 Chen Jing
!what do you learn about that particular topic?
I learn that the The bending of light that occurs when light passes from one transparent material to another is called refraction of light.light bends because its speed hanges as it moves from one transparent material to another.
light travels slower in more dense materials than in less dense materials.therefore light travels slower in glass than in air.
and i know many effects of refraction of light.such as we can use refraction of light to made the words appear to be nearer to the surface of the glass than they actually are.
From:textbook resource!
summarise the key points of that topic.
Refraction is the bending of light that takes place at a boundary between two materials having different indices of refraction.
Refraction is due to a change in the speed of light as it passes from one medium to another. The change in direction of the ray (represented by the heavy line in each diagram) is what is meant by the term refraction, which just means ¡°bending¡± or ¡°breaking.¡±
From:http://mintaka.sdsu.edu/GF/explain/optics/refr.html!
anything interesting to add?I
n 1621, a Dutch physicist named Willebrord Snell (1591-1626), derived the relationship between the different angles of light as it passes from one transperent medium to another.
When light passes from one transparent medium to another, it bends according to Snell's law which states:Ni * Sin(Ai) = Nr * Sin(Ar),
where:Ni is the refractive index of the medium the light is leaving,Ai is the incident angle between the light ray and the normal to the meduim to medium interface,Nr is the refractive index of the medium the light is entering,Ar is the refractive angle between the light ray and the normal to the meduim to medium interface.
From:http://www.ps.missouri.edu/rickspage/refract/refraction.html
I learn that the The bending of light that occurs when light passes from one transparent material to another is called refraction of light.light bends because its speed hanges as it moves from one transparent material to another.
light travels slower in more dense materials than in less dense materials.therefore light travels slower in glass than in air.
and i know many effects of refraction of light.such as we can use refraction of light to made the words appear to be nearer to the surface of the glass than they actually are.
From:textbook resource!
summarise the key points of that topic.
Refraction is the bending of light that takes place at a boundary between two materials having different indices of refraction.
Refraction is due to a change in the speed of light as it passes from one medium to another. The change in direction of the ray (represented by the heavy line in each diagram) is what is meant by the term refraction, which just means ¡°bending¡± or ¡°breaking.¡±
From:http://mintaka.sdsu.edu/GF/explain/optics/refr.html!
anything interesting to add?I
n 1621, a Dutch physicist named Willebrord Snell (1591-1626), derived the relationship between the different angles of light as it passes from one transperent medium to another.
When light passes from one transparent medium to another, it bends according to Snell's law which states:Ni * Sin(Ai) = Nr * Sin(Ar),
where:Ni is the refractive index of the medium the light is leaving,Ai is the incident angle between the light ray and the normal to the meduim to medium interface,Nr is the refractive index of the medium the light is entering,Ar is the refractive angle between the light ray and the normal to the meduim to medium interface.
From:http://www.ps.missouri.edu/rickspage/refract/refraction.html
Refraction of Light by 2E2 Tan Chew Mei
i.What is refraction of light ?
Refraction is the change in direction of a wave due to a change in its speed. This is most commonly seen when a wave passes from one medium to another. Refraction of light is the most commonly seen example, but any type of wave can refract when it interacts with a medium, for example when sound waves pass from one medium into another or when water waves move into water of a different depth. Refraction is also described by Snell’s Law.
ii.When does it happen? How will light bend ?
In optics, refraction occurs when light waves travel from a medium with a given refractive index to a medium with another. At the boundary between the media, the wave's phase velocity is altered, it changes direction, and its wave length increases or decreases but its frequency remains constant. For example, a light ray will refract as it enters and leaves glass; understanding of this concept led to the invention of lenses and the refracting telescope.
iii. What is refractive index ?
Refraction can be seen when looking into a bowl of water. Air has a refractive index of about 1.0003, and water has a refractive index of about 1.33.
Iv. Effect of refraction ?
refraction can make objects appear closer than they are, it is responsible for allowing water to magnify objects. First, as light is entering a drop of water, it slows down. If the water's surface is not flat, then the light will be bent into a new path. This round shape will bend the light outwards and as it spreads out, the image you see gets larger.
Refraction is the change in direction of a wave due to a change in its speed. This is most commonly seen when a wave passes from one medium to another. Refraction of light is the most commonly seen example, but any type of wave can refract when it interacts with a medium, for example when sound waves pass from one medium into another or when water waves move into water of a different depth. Refraction is also described by Snell’s Law.
ii.When does it happen? How will light bend ?
In optics, refraction occurs when light waves travel from a medium with a given refractive index to a medium with another. At the boundary between the media, the wave's phase velocity is altered, it changes direction, and its wave length increases or decreases but its frequency remains constant. For example, a light ray will refract as it enters and leaves glass; understanding of this concept led to the invention of lenses and the refracting telescope.
iii. What is refractive index ?
Refraction can be seen when looking into a bowl of water. Air has a refractive index of about 1.0003, and water has a refractive index of about 1.33.
Iv. Effect of refraction ?
refraction can make objects appear closer than they are, it is responsible for allowing water to magnify objects. First, as light is entering a drop of water, it slows down. If the water's surface is not flat, then the light will be bent into a new path. This round shape will bend the light outwards and as it spreads out, the image you see gets larger.
Refraction of Light by 2E1 The Su Zin
After doing research about this topic, I have learnt more concerning with the topic: refraction such as its laws and rules and also about refractive index.
1)Refraction
Refraction refers to the change in direction of light when it moves from one transparent medium into another transparent material which causes it to travel at a different speed.
Light slows down
Visible light is electromagnetic radiation or waveform. The speed or velocity of light in a vacuum is about 186,000 miles per second or 300,000 kilometres per second. The velocity of light or other electromagnetic radiation is typically slower when it passes through a transparent material. For example, the speed of light in water is about 140,000 mi/sec or 226,000 km/sec.
2)Refraction Rules When visible light passes through a transparent material such as glass and water, its velocity(speed) changes according to the index of refraction of the material. The index of refraction of air is about 1.00 and that of water is 1.33. When the beam of light enters water at an angle, it is bent or refracted as a result of the decrease in velocity.
Light is refracted inward when entering medium of higher index of refraction
Light is refracted outward when entering medium of lower index of refraction
The bending occurs because light travels more slowly in a denser medium.
Why does the light beam bend?
Considering a group of soldiers marching into a muddy field at an angle to their direction of travel can explain how a beam of light will be refracted. As the soldiers try to stay in a line, the direction of travel would bend because marching in mud would slow them down, starting with the first group to enter the field. Then, as they leave the muddy area, they go to their original speed, thus bending the direction of travel again. The original direction and the final direction are parallel but displaced.
The same thing happens when a beam of light enters a transparent material at an angle.
Example of how light is refracted when passes through different medium.
3 )INDEX OF REFRACTION
Refractive index is a number which indicates the power of refraction of a given medium relative to a previous medium. The absolute refractive index of a medium is the speed of light in a vacuum (air) divided by the speed of light in that medium.
Symbol is “n”. The larger the index ,the smaller the speed of light.
n = c/v
4)THE EFFECTS OF REFRACTION
Refraction has some unusual effects in everyday life.
-When a submerged object is viewed from above the surface of water, it appears closer to the surface than it is. This is due to light rays from the object being bent away from the normal as they pass out of the water (the more dense medium) into air (the less dense medium).
-The ratio of the real depth of the object to its apparent depth equals the refractive index of water.
Here are some examples of the EFFECTS:
eg1 - Apparent Depth in Water
In the above diagram, the chest seems to be nearer to the surface, but it is not. Refraction causes the chest to appear nearer to the surface than it actually is when it is in transparent material, water .
When you look at something under the water, not only the position of the object is not located at the place you though it was. The shape of the object is also changed. Location of the image and its shape are all depend on the location you view it.
eg2- In this diagram, the straw seems bent in the glass.
Refraction causes point X to appear nearer to the surface at Y so we see that that the straw appears to bend nearer to the surface of the water. This is one of the effect of refraction.
Eg.3 Pencil in water glass
You can also see this effect by putting a pencil in a glass of water. It appears as if the pencil is broken, but it is just because of the refraction of light.
The light from the pencil is refracted as it passes from the water to the glass to air, causing it to be displaced. Since the surface of the glass is curved, the water in the glass also acts as a magnifying glass, slightly enlarging the pencil.
So here is the link for mini short quiz, very simple quiz. =)
http://www.school-for-champions.com/science/light_refraction.htm#Mini-quiz
Acknowledgement
1 . http://sol.sci.uop.edu/~jfalward/refraction/refraction.html
2.http://sg.answers.yahoo.com/question/index;_ylt=ApfjYqHaykzhEnCDtDjBpjYh4wt.;_ylv=3?qid=20070902013243AA3gdvF
3. http://www.school-for-champions.com/science/light_refraction.htm
http://www.phy.ntnu.edu.tw/ntnujava/
4. The Usborne Illustrated Dictionary Of Physics
1)Refraction
Refraction refers to the change in direction of light when it moves from one transparent medium into another transparent material which causes it to travel at a different speed.
Light slows down
Visible light is electromagnetic radiation or waveform. The speed or velocity of light in a vacuum is about 186,000 miles per second or 300,000 kilometres per second. The velocity of light or other electromagnetic radiation is typically slower when it passes through a transparent material. For example, the speed of light in water is about 140,000 mi/sec or 226,000 km/sec.
2)Refraction Rules When visible light passes through a transparent material such as glass and water, its velocity(speed) changes according to the index of refraction of the material. The index of refraction of air is about 1.00 and that of water is 1.33. When the beam of light enters water at an angle, it is bent or refracted as a result of the decrease in velocity.
Light is refracted inward when entering medium of higher index of refraction
Light is refracted outward when entering medium of lower index of refraction
The bending occurs because light travels more slowly in a denser medium.
Why does the light beam bend?
Considering a group of soldiers marching into a muddy field at an angle to their direction of travel can explain how a beam of light will be refracted. As the soldiers try to stay in a line, the direction of travel would bend because marching in mud would slow them down, starting with the first group to enter the field. Then, as they leave the muddy area, they go to their original speed, thus bending the direction of travel again. The original direction and the final direction are parallel but displaced.
The same thing happens when a beam of light enters a transparent material at an angle.
Example of how light is refracted when passes through different medium.
3 )INDEX OF REFRACTION
Refractive index is a number which indicates the power of refraction of a given medium relative to a previous medium. The absolute refractive index of a medium is the speed of light in a vacuum (air) divided by the speed of light in that medium.
Symbol is “n”. The larger the index ,the smaller the speed of light.
n = c/v
4)THE EFFECTS OF REFRACTION
Refraction has some unusual effects in everyday life.
-When a submerged object is viewed from above the surface of water, it appears closer to the surface than it is. This is due to light rays from the object being bent away from the normal as they pass out of the water (the more dense medium) into air (the less dense medium).
-The ratio of the real depth of the object to its apparent depth equals the refractive index of water.
Here are some examples of the EFFECTS:
eg1 - Apparent Depth in Water
In the above diagram, the chest seems to be nearer to the surface, but it is not. Refraction causes the chest to appear nearer to the surface than it actually is when it is in transparent material, water .
When you look at something under the water, not only the position of the object is not located at the place you though it was. The shape of the object is also changed. Location of the image and its shape are all depend on the location you view it.
eg2- In this diagram, the straw seems bent in the glass.
Refraction causes point X to appear nearer to the surface at Y so we see that that the straw appears to bend nearer to the surface of the water. This is one of the effect of refraction.
Eg.3 Pencil in water glass
You can also see this effect by putting a pencil in a glass of water. It appears as if the pencil is broken, but it is just because of the refraction of light.
The light from the pencil is refracted as it passes from the water to the glass to air, causing it to be displaced. Since the surface of the glass is curved, the water in the glass also acts as a magnifying glass, slightly enlarging the pencil.
So here is the link for mini short quiz, very simple quiz. =)
http://www.school-for-champions.com/science/light_refraction.htm#Mini-quiz
Acknowledgement
1 . http://sol.sci.uop.edu/~jfalward/refraction/refraction.html
2.http://sg.answers.yahoo.com/question/index;_ylt=ApfjYqHaykzhEnCDtDjBpjYh4wt.;_ylv=3?qid=20070902013243AA3gdvF
3. http://www.school-for-champions.com/science/light_refraction.htm
http://www.phy.ntnu.edu.tw/ntnujava/
4. The Usborne Illustrated Dictionary Of Physics
Colours of Light by 2E1 Jason
Colour:
Colour is the visual perceptual property corresponding in humans to the categories called red, yellow, blue, black, etc. Colour derives from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors.
White light is a mixture of different colours and when it passes through a glass prism, the light splits up into the colours you see in a rainbow. Spectrum, (white light) consists of Red, Orange, Yellow, Green, Blue, Indigo and Violet. The separation of splitting of white light into its separate colours is known as ‘Dispersion’. The colours of the spectrum can be recombined by using a second prism or spinning a colour wheel, we can get white light.
Mixing Coloured Lights
The primary colours of light are red, blue, and green. You can get white light or any other colour by mixing just three colours. If you mix two primary colours at a time, you will get magenta, yellow, and cyan.
Colour Filters
Colour filter is the clear plastic or glass which only lets through some of the colours meanwhile the other colours is being absorbed.
When white light (spectrum) shines on a coloured object, some of the colours in the spectrum are reflected and some are being absorbed. We can see the colour that is reflected light.
Credits:
http://en.wikipedia.org/wiki/Colour
http://wolfstone.halloweenhost.com/Lighting/colmix_ColorMixing.html
Explore Your World with SCIENCE DISCOVERY 2 [Chapter 8.4, colour]
Colour is the visual perceptual property corresponding in humans to the categories called red, yellow, blue, black, etc. Colour derives from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors.
White light is a mixture of different colours and when it passes through a glass prism, the light splits up into the colours you see in a rainbow. Spectrum, (white light) consists of Red, Orange, Yellow, Green, Blue, Indigo and Violet. The separation of splitting of white light into its separate colours is known as ‘Dispersion’. The colours of the spectrum can be recombined by using a second prism or spinning a colour wheel, we can get white light.
Mixing Coloured Lights
The primary colours of light are red, blue, and green. You can get white light or any other colour by mixing just three colours. If you mix two primary colours at a time, you will get magenta, yellow, and cyan.
Colour Filters
Colour filter is the clear plastic or glass which only lets through some of the colours meanwhile the other colours is being absorbed.
When white light (spectrum) shines on a coloured object, some of the colours in the spectrum are reflected and some are being absorbed. We can see the colour that is reflected light.
Credits:
http://en.wikipedia.org/wiki/Colour
http://wolfstone.halloweenhost.com/Lighting/colmix_ColorMixing.html
Explore Your World with SCIENCE DISCOVERY 2 [Chapter 8.4, colour]
Colours of Light by 2E4 Jeremy Lim
In this topic I have learn about how colours are produce , what is dispersion of light and to recombine colours back after spitting them and also what is the effect of mixing colours as well as what is primary colours.
White light which is also known as ordinary light actually is a mixture of different colours. And when that white light pass through a glass prism the light actually spits up into 7 different colours and that process is call dispersion.
The spectrum consist of 7 beautiful colours, they are red, orange, yellow, green, blue, indigo, violet. It is also difficult to say when one colours ends or start as these colours merge into one another gradually.
The reason why there is always (maybe) a rainbow after a shower of rain is because the raindrops act like small prism and when sunlight passes through them …. They form the colours of the spectrum.
And since we are able to separate those seven colours from the spectrum, thus we are also able to rejoin the seven colours back into white light. And in order to do that is 2 ways.
The first way is to add in another prism or to spin a colour wheel and another
name for the colour wheel is call a Newton disc.
Lights of different colours can be mixed together to produce other colours and in fact white light and light of other colours can be obtained by mixing 3 colours, these colours are red, blue , green. These colours are called primary colours.
Here are the *formula* of colours, red + blue = magenta, red+ green = yellow, blue + green = cyan. And by adding the 3 primary we get white colours.
Clear plastic or glass only let through some colours and the other colours are absorbed are call colour filter. When white light shines on a coloured object, some colour are reflected and some are absorbed.
To end my project work, I want to say that the colour of an object is the colour of the light that is reflected from it into our eyes. And if no light is reflected the object would be black. Black is not a colour it is just something that indicates the absence of light.
Text book resource*
White light which is also known as ordinary light actually is a mixture of different colours. And when that white light pass through a glass prism the light actually spits up into 7 different colours and that process is call dispersion.
The spectrum consist of 7 beautiful colours, they are red, orange, yellow, green, blue, indigo, violet. It is also difficult to say when one colours ends or start as these colours merge into one another gradually.
The reason why there is always (maybe) a rainbow after a shower of rain is because the raindrops act like small prism and when sunlight passes through them …. They form the colours of the spectrum.
And since we are able to separate those seven colours from the spectrum, thus we are also able to rejoin the seven colours back into white light. And in order to do that is 2 ways.
The first way is to add in another prism or to spin a colour wheel and another
name for the colour wheel is call a Newton disc.
Lights of different colours can be mixed together to produce other colours and in fact white light and light of other colours can be obtained by mixing 3 colours, these colours are red, blue , green. These colours are called primary colours.
Here are the *formula* of colours, red + blue = magenta, red+ green = yellow, blue + green = cyan. And by adding the 3 primary we get white colours.
Clear plastic or glass only let through some colours and the other colours are absorbed are call colour filter. When white light shines on a coloured object, some colour are reflected and some are absorbed.
To end my project work, I want to say that the colour of an object is the colour of the light that is reflected from it into our eyes. And if no light is reflected the object would be black. Black is not a colour it is just something that indicates the absence of light.
Text book resource*
Refraction of Light by 2E1 Shahir
For thousands of years, people have noticed that a straight stick placed obliquely in water appears to be broken at an angle where it enters the water. This is the origin of the term "refraction," which means literally "broken back."
Refraction is the change of light that changes direction when it passes from one medium to another.
refraction occurs when light waves travel from a medium with a given refractive index to a medium with another.
At the boundary between the media, the wave's phase velocity is altered, it changes direction, and its wavelength increases or decreases but its frequency remains constant.
For example, a light ray will refract as it enters and leaves glass.the understanding of this concept led to the invention of lenses and the refracting telescope
from a less dense material to a denser material, light will slows down and refracted towards the normal, while from denser material into a less dense material, light speeds up and is refracted away from the normal.
The refractive index of a transparent optical medium, also called the index of refraction, is the factor by which the phase velocity is decreased relative to the velocity of light in vacuum, assuming linear propagation
effects of refraction are : -it causes an object to be nearer than it actually is when a transparent material is on top - a stick will appear to be bent inside a bearker filled with water.
From this topic, i have learned that refraction happens in our everyday life. It causes effects that are very unusual and refraction is an interesting topic to learn.
key points : -refraction happens when light changes direction when it passes from one medium to another -it causes effects that are unusual.
Refraction is the change of light that changes direction when it passes from one medium to another.
refraction occurs when light waves travel from a medium with a given refractive index to a medium with another.
At the boundary between the media, the wave's phase velocity is altered, it changes direction, and its wavelength increases or decreases but its frequency remains constant.
For example, a light ray will refract as it enters and leaves glass.the understanding of this concept led to the invention of lenses and the refracting telescope
from a less dense material to a denser material, light will slows down and refracted towards the normal, while from denser material into a less dense material, light speeds up and is refracted away from the normal.
The refractive index of a transparent optical medium, also called the index of refraction, is the factor by which the phase velocity is decreased relative to the velocity of light in vacuum, assuming linear propagation
effects of refraction are : -it causes an object to be nearer than it actually is when a transparent material is on top - a stick will appear to be bent inside a bearker filled with water.
From this topic, i have learned that refraction happens in our everyday life. It causes effects that are very unusual and refraction is an interesting topic to learn.
key points : -refraction happens when light changes direction when it passes from one medium to another -it causes effects that are unusual.
Reflection of light by 2E3 Huang Yue
What is reflection ???????
The bouncing of light off a mirror surface is called reflection.
Types of reflection?????
There are two types of reflection --regular reflection , diffuse reflection.
--When a parallel beam of light hits a smooth surface,it would be reflected as a parallel beam .This is called regular reflection.
--When a beam of light hits a rough surface,the individual rays are reflectedin different directions,then no image formed .This types of reflection is called diffuse reflection.
Uses of reflection of light,examples?
Uses of plane mirrors -----
—— the rear of a view mirror of a car can helps to see traffic behind the car.
——plane mirrors on walls makes a room brighter.
——people use plane mirrors to check their appearance.
Uses of curved mirrors----
——security mirrors are used in shops.
——blind corner mirrors helped driver to see objects around the corner.
——a concave mirror is used to reflect light into microscope.
Acknowledgements:
----Explore your world with science discovery 2
-----http://images.google.cn/imgres?imgurl=http://id.mind.net/~zona/mstm/physics/light/rayOptics/reflection/r1.jpg&imgrefurl=http://id.mind.net/~zona/mstm/physics/light/rayOptics/reflection/reflection1.html&h=300&w=400&sz=14&hl=zh-CN&start=17&um=1&tbnid=vcnBWStV9c6jCM:&tbnh=93&tbnw=124&prev=/images%3Fq%3Dreflection%2Bof%2Blight%26um%3D1%26complete%3D1%26hl%3Dzh-CN%26rlz%3D1T4XNLA_zh-CNSG277SG277%26sa%3DX
The bouncing of light off a mirror surface is called reflection.
Types of reflection?????
There are two types of reflection --regular reflection , diffuse reflection.
--When a parallel beam of light hits a smooth surface,it would be reflected as a parallel beam .This is called regular reflection.
--When a beam of light hits a rough surface,the individual rays are reflectedin different directions,then no image formed .This types of reflection is called diffuse reflection.
Uses of reflection of light,examples?
Uses of plane mirrors -----
—— the rear of a view mirror of a car can helps to see traffic behind the car.
——plane mirrors on walls makes a room brighter.
——people use plane mirrors to check their appearance.
Uses of curved mirrors----
——security mirrors are used in shops.
——blind corner mirrors helped driver to see objects around the corner.
——a concave mirror is used to reflect light into microscope.
Acknowledgements:
----Explore your world with science discovery 2
-----http://images.google.cn/imgres?imgurl=http://id.mind.net/~zona/mstm/physics/light/rayOptics/reflection/r1.jpg&imgrefurl=http://id.mind.net/~zona/mstm/physics/light/rayOptics/reflection/reflection1.html&h=300&w=400&sz=14&hl=zh-CN&start=17&um=1&tbnid=vcnBWStV9c6jCM:&tbnh=93&tbnw=124&prev=/images%3Fq%3Dreflection%2Bof%2Blight%26um%3D1%26complete%3D1%26hl%3Dzh-CN%26rlz%3D1T4XNLA_zh-CNSG277SG277%26sa%3DX
Colours of Light by 2E4 Jun Min Jung
How are colours being produced?
Colours are produced because of sun light(white light).
What is Dispersion of light?
The speed of light is slower in various than it is in a vacuum or outer space. When the light passes into a material at an angle, the light beam is bent or refracted according to Snell’s Law and the index of retraction of the material. But also, the speed of light through a material varies slightly with the wavelength or frequency of the light. Thus, each wavelength is refracted at a slightly different angle when passing through a material at an angle. This spreading out of the beam of light is called dispersion. This can be seen when sunlight passes through a glass prism.
How to get rainbow colours and to recombine colours again?
Rainbow is formed when sunlight (white light) passes through raindrops. Tiny droplets of water refract the white light from the sun and create a spectrum of colours similar to what happen in a prism. Since the droplets are spheres, the light is reflected internally in the droplets and the rainbow returns toward the direction of the light.
Since white light consists of seven colours, we should be able to get white light again by combining the colours together. There are two ways to recombine the colours.
• By using a second prism: When another prism is placed, the colours recombine.
• Spinning a colour wheel (also called a Newton’s disc\): When the wheel is turned quickly, the colours appear to mix and the wheel looks white.
What is primary colours?
Light of different colours can be mixed together to produce other colours. In fact, white light and other light of colours – red, blue and green. These three colours are called the primary colours.
Effects of Mixing of Colours
Mixing the primary colours two at a time gives the following colours:
• red + blue = green
• red + green = yellow
• blue + green = cyan
Mixing all three primary colours gives white light. That is:
• red + blue + green = white
http://www.school-for-champions.com/science/light_dispersion.htm
Textbook - p.128~p.130
Colours are produced because of sun light(white light).
What is Dispersion of light?
The speed of light is slower in various than it is in a vacuum or outer space. When the light passes into a material at an angle, the light beam is bent or refracted according to Snell’s Law and the index of retraction of the material. But also, the speed of light through a material varies slightly with the wavelength or frequency of the light. Thus, each wavelength is refracted at a slightly different angle when passing through a material at an angle. This spreading out of the beam of light is called dispersion. This can be seen when sunlight passes through a glass prism.
How to get rainbow colours and to recombine colours again?
Rainbow is formed when sunlight (white light) passes through raindrops. Tiny droplets of water refract the white light from the sun and create a spectrum of colours similar to what happen in a prism. Since the droplets are spheres, the light is reflected internally in the droplets and the rainbow returns toward the direction of the light.
Since white light consists of seven colours, we should be able to get white light again by combining the colours together. There are two ways to recombine the colours.
• By using a second prism: When another prism is placed, the colours recombine.
• Spinning a colour wheel (also called a Newton’s disc\): When the wheel is turned quickly, the colours appear to mix and the wheel looks white.
What is primary colours?
Light of different colours can be mixed together to produce other colours. In fact, white light and other light of colours – red, blue and green. These three colours are called the primary colours.
Effects of Mixing of Colours
Mixing the primary colours two at a time gives the following colours:
• red + blue = green
• red + green = yellow
• blue + green = cyan
Mixing all three primary colours gives white light. That is:
• red + blue + green = white
http://www.school-for-champions.com/science/light_dispersion.htm
Textbook - p.128~p.130
Colours of Light by 2E1 Vaishnavi
In this essay I am going to explain about our physics project. My topic was colours. From the project we have understood many things about colours.
Colour is simply light of different wavelengths and frequencies and light is just one form of energy that we can actually see.
The three primary colours are red, green and blue. Colour comes from light.
To see the colour physically we need to have a prism. When light from the sun passes through a prism, the light is split into the seven visible colours by refraction.
Refraction is caused by the change in speed experienced by a wave of light when it changes medium. The amount of energy in a given light wave is proportionally related to its frequency, thus a high frequency light wave has a higher energy than that of a low frequency.
Each colour has its own particular wavelength and frequency. Each colour can be measured in units of cycles or waves per second. The frequency of a wave is determined by the number of complete waves, or wavelengths, that pass a given point each second.
Higher frequency colours are - violet - indigo - blue lower frequency colours are - yellow - orange - red.
A high frequency light wave has a higher energy than that of a low frequency light wave.
Refraction of Light by 2E1 Fatima
What is refraction?
Refraction is the bending of a light when it passes from one transparent medium into another.
When and how does it happen?
Light changes direction because light travels at different speeds in different substances, causing it to be bent when it changes from one substance to another.
The degree of refraction depends in part on the angle at which the light hits the surface of a material. A line perpendicular to that surface is called the normal. The angle between the incoming light ray and the normal to the surface is called the angle of incidence. The angle between the refracted ray and the normal is called the angle of refraction. The angle of refraction cannot exceed 90°.
A ray of light refracts or deviates from its original path as it passes from one optical medium to another because the speed of light changes.
Refractive Index?
The amount of refraction can be found using the refractive index.
The speed at which light travels may change as it passes from one medium to another. Different substances will cause different changes to the speed of light. For example, glass slows light more than water.
To find the effect of a substance we can calculate its refractive index. This is a ratio of the speed of light in air or vacuum and the speed of light in the substance.
refractive index = speed of light in air/speed of light in substance
For example, the speed of light in air is 300,000 km/s and in glass it travels at about 200,000 km/s. Its refractive index is therefore 1.5. Water, however, has a refractive index of 1.33. This means that light rays are refracted more when they enter glass than when they enter water.
Effects of Refraction?
The effects of refraction:
1. Make things appear to be nearer
2. make objects in water appear to be bent
the pencil appears to be bent because of refraction
DK Reference Encyclopedia
http://www.tutorvista.com/content/physics/physics-ii/light-refraction/refraction-light.php
http://images.google.com.sg/
Refraction is the bending of a light when it passes from one transparent medium into another.
When and how does it happen?
Light changes direction because light travels at different speeds in different substances, causing it to be bent when it changes from one substance to another.
The degree of refraction depends in part on the angle at which the light hits the surface of a material. A line perpendicular to that surface is called the normal. The angle between the incoming light ray and the normal to the surface is called the angle of incidence. The angle between the refracted ray and the normal is called the angle of refraction. The angle of refraction cannot exceed 90°.
A ray of light refracts or deviates from its original path as it passes from one optical medium to another because the speed of light changes.
Refractive Index?
The amount of refraction can be found using the refractive index.
The speed at which light travels may change as it passes from one medium to another. Different substances will cause different changes to the speed of light. For example, glass slows light more than water.
To find the effect of a substance we can calculate its refractive index. This is a ratio of the speed of light in air or vacuum and the speed of light in the substance.
refractive index = speed of light in air/speed of light in substance
For example, the speed of light in air is 300,000 km/s and in glass it travels at about 200,000 km/s. Its refractive index is therefore 1.5. Water, however, has a refractive index of 1.33. This means that light rays are refracted more when they enter glass than when they enter water.
Effects of Refraction?
The effects of refraction:
1. Make things appear to be nearer
2. make objects in water appear to be bent
the pencil appears to be bent because of refraction
DK Reference Encyclopedia
http://www.tutorvista.com/content/physics/physics-ii/light-refraction/refraction-light.php
http://images.google.com.sg/
Electricity by 2E1 Darren Tan
What is electricity?
Electricity is a form of energy. Electricity is the flow of electrons. All matter is made up of atoms, and an atom has a center, called a nucleus. The nucleus contains positively charged particles called protons and uncharged particles called neutrons. The nucleus of an atom is surrounded by negatively charged particles called electrons. The negative charge of an electron is equal to the positive charge of a proton, and the number of electrons in an atom is usually equal to the number of protons.
How is electricity produce?
An electric generator is a device for converting mechanical energy into electrical energy. The process is based on the relationship between magnetism and electricity. When a wire or any other electrically conductive material moves across a magnetic field, an electric current occurs in the wire. The large generators used by the electric utility industry have a stationary conductor. A magnet attached to the end of a rotating shaft is positioned inside a stationary conducting ring that is wrapped with a long, continuous piece of wire. When the magnet rotates, it induces a small electric current in each section of wire as it passes. This current is what is used for electric power.
How are electricity used?
Electricity are used in many thing including computer that we used, oven that we use to warm up food, light that help us to see better, hand phone that let us contact other ETC.
Electricity is a form of energy. Electricity is the flow of electrons. All matter is made up of atoms, and an atom has a center, called a nucleus. The nucleus contains positively charged particles called protons and uncharged particles called neutrons. The nucleus of an atom is surrounded by negatively charged particles called electrons. The negative charge of an electron is equal to the positive charge of a proton, and the number of electrons in an atom is usually equal to the number of protons.
How is electricity produce?
An electric generator is a device for converting mechanical energy into electrical energy. The process is based on the relationship between magnetism and electricity. When a wire or any other electrically conductive material moves across a magnetic field, an electric current occurs in the wire. The large generators used by the electric utility industry have a stationary conductor. A magnet attached to the end of a rotating shaft is positioned inside a stationary conducting ring that is wrapped with a long, continuous piece of wire. When the magnet rotates, it induces a small electric current in each section of wire as it passes. This current is what is used for electric power.
How are electricity used?
Electricity are used in many thing including computer that we used, oven that we use to warm up food, light that help us to see better, hand phone that let us contact other ETC.
Refraction of Light by 2E1 Emily
REFRACTION.
If you have ever half submerged a straight stick into water, you have probably noticed that the stick appears bent at the point it enters the water.This optical effect is due to refraction.
Refraction is the change in direction of a wave due to a change in its speed.
Refraction happens when light passes from one medium to another.
When light passes from one medium to another, light from less dense media to a denser media will slow down and it is refracted towards the normal. But when light passes from denser media to less dense media, it will speeds up and it is refracted from the normal.
REFRACTIVE INDEX
The refractive index of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium.
EFFECTS OF REFRACTION
refraction has some unusual effects in everyday life. some examples are :
- when you place a glass block on top of your textbook, and observe. The words will appear to be nearer to the surface of the glass than they actually are.
- the object appears to be at a higher position than it actually is. for this reason, a swimming pool appears shallower than it really is.
- a pencil inside a beaker filled with water will appear to be bent.
From all the information i have gained, i have learnt that refraction occurs in everyday life. It is very interesting to know how it happens and what are the unusual effects caused by refraction.
The Key point of this topic is : Refraction happens when light changes direction when it passes from one transparent material into another. Refraction will cause an object appears to be at higher position than it actually is.
Science Textbook Chapter 8, Refraction. http://www.ps.missouri.edu/rickspage/refract/refraction.html http://en.wikipedia.org/wiki/Refraction
If you have ever half submerged a straight stick into water, you have probably noticed that the stick appears bent at the point it enters the water.This optical effect is due to refraction.
Refraction is the change in direction of a wave due to a change in its speed.
Refraction happens when light passes from one medium to another.
When light passes from one medium to another, light from less dense media to a denser media will slow down and it is refracted towards the normal. But when light passes from denser media to less dense media, it will speeds up and it is refracted from the normal.
REFRACTIVE INDEX
The refractive index of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium.
EFFECTS OF REFRACTION
refraction has some unusual effects in everyday life. some examples are :
- when you place a glass block on top of your textbook, and observe. The words will appear to be nearer to the surface of the glass than they actually are.
- the object appears to be at a higher position than it actually is. for this reason, a swimming pool appears shallower than it really is.
- a pencil inside a beaker filled with water will appear to be bent.
From all the information i have gained, i have learnt that refraction occurs in everyday life. It is very interesting to know how it happens and what are the unusual effects caused by refraction.
The Key point of this topic is : Refraction happens when light changes direction when it passes from one transparent material into another. Refraction will cause an object appears to be at higher position than it actually is.
Science Textbook Chapter 8, Refraction. http://www.ps.missouri.edu/rickspage/refract/refraction.html http://en.wikipedia.org/wiki/Refraction
Reflection of Light by 2E2 Zin Win
Reflection on a mirror surface.
I have learnt that reflection is the bouncing off light after hitting a mirror surfaces.
There are two type of reflection the 1st one is regular reflection and 2nd is the diffused reflection. Regular reflection is made out of a parallel beam of light which bounce off a smooth surface and an image is form while the diffuse reflection reflects on a rough surface the ray is reflected in different direction and no image is form.
The angle of incidence is equal to the angles of reflection in the plane mirror
Properties of plane mirror:
Virtual
Upright
Same size as the object
Laterally inverted
Uses of plane mirror :
helps a driver see the traffic behind ,
help a person check appearance
make a room bigger
periscope are made of two plane mirrors to see over obstacles
Convex mirrors from upright image that is always smaller than the object. They allow many things to be seen
Concave mirrors formed upright magnified images if the object is close to the mirror. If the image is further away, the image is inverted
I have learnt that reflection is the bouncing off light after hitting a mirror surfaces.
There are two type of reflection the 1st one is regular reflection and 2nd is the diffused reflection. Regular reflection is made out of a parallel beam of light which bounce off a smooth surface and an image is form while the diffuse reflection reflects on a rough surface the ray is reflected in different direction and no image is form.
The angle of incidence is equal to the angles of reflection in the plane mirror
Properties of plane mirror:
Virtual
Upright
Same size as the object
Laterally inverted
Uses of plane mirror :
helps a driver see the traffic behind ,
help a person check appearance
make a room bigger
periscope are made of two plane mirrors to see over obstacles
Convex mirrors from upright image that is always smaller than the object. They allow many things to be seen
Concave mirrors formed upright magnified images if the object is close to the mirror. If the image is further away, the image is inverted
Electricity by 2E4 Chanchai Kovitpornsin
Name class 2E4 index no. 18
Electricity
I have learnt electricity is a form of energy. It is very convenient because it be changed to other forms of energy.
How electricity produced
I have learnt electricity energy comes from 2 main sources. There are electricity and electricity cells.
Main electricity is generated in power station. The plugs of electricity appliances are inserted into mains sockets to obtain this electricity. Main electricity supplies a lot of energy.
Electricity cells give out only a little energy. They are used in many portable electrical devices and safe to use.
Electric Circuits
I have learnt to make an electrical appliance work, electricity must flow through it. The flow of electricity is called an electric current. An electric current flow only when there is: 1. A source of electrical energy and 2. A closed circuit.
Electric Current
I have learnt an electric current is the flow of electrons in one direction in a circuit.
Measuring Electric Current
I have learnt to measure the electric current, we use an ammeter.
The SI unit for electric current is the ampere (A). Smaller currents can be measured in milliamperes (mA)
1 A = 1000 mA
1 mA= 1/1000 A (or 0.001 A)
Voltage
I have learnt voltage is a measure of how much energy the electrons receive. To measure voltage we use a voltmeter.
The SI for voltage is the volt (V).
Used of electricity
Electrical energy is changed to sound energy in radios.
Electrical energy is changed to heat energy in rice cookers.
Electrical energy is changed to kinetic energy in electric fans.
Key points
Electricity is a form of energy.
Electricity energy comes from 2 main sources. There are electricity and electricity cells.
The flow of electricity is called an electric current. An electric current flow only when there is: 1. A source of electrical energy and 2. A closed circuit.
An electric current is the flow of electrons in one direction in a circuit
Voltage is a measure of how much energy the electrons receive. To measure voltage we use a voltmeter.
History
That certain objects such as rods of amber could be rubbed with cat's fur and attract light objects like feathers was known to ancient cultures around the Mediterranean. Thales of Miletos conducted a series of experiments into static electricity around 600 BC, from which he believed that friction rendered amber magnetic, in contrast to minerals such as magnetite, which needed no rubbing. Thales was incorrect in believing the attraction was due to a magnetic effect, but later science would prove a link between magnetism and electricity.
Information
http://en.wikipedia.org/wiki/Electricity
Science Discovery 2 textbook
Electricity
I have learnt electricity is a form of energy. It is very convenient because it be changed to other forms of energy.
How electricity produced
I have learnt electricity energy comes from 2 main sources. There are electricity and electricity cells.
Main electricity is generated in power station. The plugs of electricity appliances are inserted into mains sockets to obtain this electricity. Main electricity supplies a lot of energy.
Electricity cells give out only a little energy. They are used in many portable electrical devices and safe to use.
Electric Circuits
I have learnt to make an electrical appliance work, electricity must flow through it. The flow of electricity is called an electric current. An electric current flow only when there is: 1. A source of electrical energy and 2. A closed circuit.
Electric Current
I have learnt an electric current is the flow of electrons in one direction in a circuit.
Measuring Electric Current
I have learnt to measure the electric current, we use an ammeter.
The SI unit for electric current is the ampere (A). Smaller currents can be measured in milliamperes (mA)
1 A = 1000 mA
1 mA= 1/1000 A (or 0.001 A)
Voltage
I have learnt voltage is a measure of how much energy the electrons receive. To measure voltage we use a voltmeter.
The SI for voltage is the volt (V).
Used of electricity
Electrical energy is changed to sound energy in radios.
Electrical energy is changed to heat energy in rice cookers.
Electrical energy is changed to kinetic energy in electric fans.
Key points
Electricity is a form of energy.
Electricity energy comes from 2 main sources. There are electricity and electricity cells.
The flow of electricity is called an electric current. An electric current flow only when there is: 1. A source of electrical energy and 2. A closed circuit.
An electric current is the flow of electrons in one direction in a circuit
Voltage is a measure of how much energy the electrons receive. To measure voltage we use a voltmeter.
History
That certain objects such as rods of amber could be rubbed with cat's fur and attract light objects like feathers was known to ancient cultures around the Mediterranean. Thales of Miletos conducted a series of experiments into static electricity around 600 BC, from which he believed that friction rendered amber magnetic, in contrast to minerals such as magnetite, which needed no rubbing. Thales was incorrect in believing the attraction was due to a magnetic effect, but later science would prove a link between magnetism and electricity.
Information
http://en.wikipedia.org/wiki/Electricity
Science Discovery 2 textbook
Sound by 2E1 Shafiatul
What is sound?
Sound is a vibration or a wave of air molecules which is caused by the motion of an object. The density of the molecules is higher when there is a compression wave. This compression wave travels through the air at the speed depending on the temperature of the surroundings. Since a sound wave contain energy which means it can make things move. But, if the sound wave hits something solid, the wave will bounce back forming an echo. Sound cannot travel through a vacuum. It can only travel through solids, liquids, gases and plasmas.
How is sound being produced?
Sound waves
A series of compressions and rarefactions which changes or waves through the air is called a sound wave. Sound waves vibrate at different rates or frequencies as they move through the air. Frequency is measured in cycles per second, or Hertz (Hz). The faster an object vibrates the higher the pitch of the sound. A frequency of 100 Hz means 100 vibrations every second.
Echolocation
The sound which travels to the walls and is reflected back to our ears is called an echo. Echoes are used to find objects underwater, to find large shoals of fish and to measure the depth of the sea. Animals use echoes to find food and to ‘see’ where they are going. For example, bats. They have a poor sense of sight but a good sense of hearing. They use echolocation to find food. Bats produce a high frequency sound to find insects to eat. This sound then reflects off the insect and travel back to the bat’s ears. This helps the bat to find even the smallest insect. Echolocation also helps the bat to ‘see’ where it is flying.
What affects sound?
Sound vibration
When an object moves or vibrates, sound is produced. There could be no sound without movement. When an object moves or vibrates, the air molecules around it will also vibrate. As long as they are not in a vacuum, vibrating objects produce sound. Each molecule moves back and forwards only in a tiny distance which is enough to cause the air particles to bump into each other. This will create areas where there are many molecules pushed closer. This is called compression. Areas where molecules are spread far apart are called rarefactions. Compressions and rarefactions move outwards away from the sound source in circles.
The speed of sound
Sound will take time to travel. In air, sound travels at a speed of 330 metres per second. In fresh water, sound travels at a speed of 150 metres per second. Sound travels at even higher speeds in solids. For example, an iron sound travels at 5000 metres per second. So, the speed of sound depends on density. The denser the material is the faster the speed of sound.
Examples of stuff producing sound
Here are some examples of things that produce sound:
-A guitar
-A trumpet
-A drum
-A bee (buzzing sound caused by its wings)
-A recorder
-Cars
-Airplanes
And many more.
Sources
http://www.sciencetech.technomuses.ca/english/schoolzone/Info_Sound.cfm
Explore your world with Science discovery 2 (pages 202-206)
http://en.wikipedia.org/wiki/Sound
Sound is a vibration or a wave of air molecules which is caused by the motion of an object. The density of the molecules is higher when there is a compression wave. This compression wave travels through the air at the speed depending on the temperature of the surroundings. Since a sound wave contain energy which means it can make things move. But, if the sound wave hits something solid, the wave will bounce back forming an echo. Sound cannot travel through a vacuum. It can only travel through solids, liquids, gases and plasmas.
How is sound being produced?
Sound waves
A series of compressions and rarefactions which changes or waves through the air is called a sound wave. Sound waves vibrate at different rates or frequencies as they move through the air. Frequency is measured in cycles per second, or Hertz (Hz). The faster an object vibrates the higher the pitch of the sound. A frequency of 100 Hz means 100 vibrations every second.
Echolocation
The sound which travels to the walls and is reflected back to our ears is called an echo. Echoes are used to find objects underwater, to find large shoals of fish and to measure the depth of the sea. Animals use echoes to find food and to ‘see’ where they are going. For example, bats. They have a poor sense of sight but a good sense of hearing. They use echolocation to find food. Bats produce a high frequency sound to find insects to eat. This sound then reflects off the insect and travel back to the bat’s ears. This helps the bat to find even the smallest insect. Echolocation also helps the bat to ‘see’ where it is flying.
What affects sound?
Sound vibration
When an object moves or vibrates, sound is produced. There could be no sound without movement. When an object moves or vibrates, the air molecules around it will also vibrate. As long as they are not in a vacuum, vibrating objects produce sound. Each molecule moves back and forwards only in a tiny distance which is enough to cause the air particles to bump into each other. This will create areas where there are many molecules pushed closer. This is called compression. Areas where molecules are spread far apart are called rarefactions. Compressions and rarefactions move outwards away from the sound source in circles.
The speed of sound
Sound will take time to travel. In air, sound travels at a speed of 330 metres per second. In fresh water, sound travels at a speed of 150 metres per second. Sound travels at even higher speeds in solids. For example, an iron sound travels at 5000 metres per second. So, the speed of sound depends on density. The denser the material is the faster the speed of sound.
Examples of stuff producing sound
Here are some examples of things that produce sound:
-A guitar
-A trumpet
-A drum
-A bee (buzzing sound caused by its wings)
-A recorder
-Cars
-Airplanes
And many more.
Sources
http://www.sciencetech.technomuses.ca/english/schoolzone/Info_Sound.cfm
Explore your world with Science discovery 2 (pages 202-206)
http://en.wikipedia.org/wiki/Sound
Refraction of Light by 2E1 Lee Jae Woong
Refraction
Through our project, I have learnt about refraction and its uses. Refraction refers to the bending of light as it passes between materials of different optical density.
In refraction, I learnt that the denser the material is, the slower the speed of light will be in that material. Refraction will happen when light passes from one medium to another medium with different densities.
For example, when light passes from air to a transparent glass block, the speed of light will slow down and it will cause the light ay to bend closer to the normal.
As seen in diagram 1, the light ray passes from air to a transparent glass block. The light ray, as shown, is bent towards the normal. This indicates that the speed of light is reduced when passing from one medium to another. The denser the medium is, the light ray will bend closer towards the normal. Similarly, when the light ray moves from glass block to air it is refracted away from the normal
Refractive Index
The refractive index of a medium is the measurement of how much the speed of light has reduced or increased inside various types of medium. Generally, the refractive index is subject to changes based on the incidence of the light. This explains why different colours of light travel at different speeds. The higher the index, the slower the speed of light will be through the medium.
Formula for refractive Index is n= sin i / sin r
Effects of Refraction
Effects of refraction can be seen in our everyday lives.
Firstly, refraction causes objects to appear closer than it actually is. For example, in a swimming pool, the pool looks shallower than it actually is. This is because our brains think the light has moved in a straight line. Therefore the swimming pool seems shallower than it usually is. Another example, is when we place our hand below a glass block, our hand seems nearer to the surface than it is. Thus the glass block seems thinner than the actual thickness.
As seen in diagram 2 the pool seems to be of equal depth and it looks shallow. However it is actually deeper than it looks. Due to refraction, swimming pools or ponds always appear to be shallower than they really are. When approaching air from water, the waves speed up and as a result they refract away from the normal.
Diverging rays enter the eye and the brain traces these rays back to where it thinks an image is. This results in a virtual image at a shallower depth than is the actual case.
References
1. Refraction of Light by Rick Reed http://www.ps.missouri.edu/rickspage/refract/refraction.html
2. Explore your world with Science Discovery 2 Textbook
3. Answers.Com http://www.answers.com/topic/refractive-index?cat=technology
4. http://www.asiatravel.com/turkey/istanbul/marinprincesskumburgaz/gifs/pool2.jpg
5. http://pachome2.pacific.net.sg/~ezzychan/refraction.htm
Through our project, I have learnt about refraction and its uses. Refraction refers to the bending of light as it passes between materials of different optical density.
In refraction, I learnt that the denser the material is, the slower the speed of light will be in that material. Refraction will happen when light passes from one medium to another medium with different densities.
For example, when light passes from air to a transparent glass block, the speed of light will slow down and it will cause the light ay to bend closer to the normal.
As seen in diagram 1, the light ray passes from air to a transparent glass block. The light ray, as shown, is bent towards the normal. This indicates that the speed of light is reduced when passing from one medium to another. The denser the medium is, the light ray will bend closer towards the normal. Similarly, when the light ray moves from glass block to air it is refracted away from the normal
Refractive Index
The refractive index of a medium is the measurement of how much the speed of light has reduced or increased inside various types of medium. Generally, the refractive index is subject to changes based on the incidence of the light. This explains why different colours of light travel at different speeds. The higher the index, the slower the speed of light will be through the medium.
Formula for refractive Index is n= sin i / sin r
Effects of Refraction
Effects of refraction can be seen in our everyday lives.
Firstly, refraction causes objects to appear closer than it actually is. For example, in a swimming pool, the pool looks shallower than it actually is. This is because our brains think the light has moved in a straight line. Therefore the swimming pool seems shallower than it usually is. Another example, is when we place our hand below a glass block, our hand seems nearer to the surface than it is. Thus the glass block seems thinner than the actual thickness.
As seen in diagram 2 the pool seems to be of equal depth and it looks shallow. However it is actually deeper than it looks. Due to refraction, swimming pools or ponds always appear to be shallower than they really are. When approaching air from water, the waves speed up and as a result they refract away from the normal.
Diverging rays enter the eye and the brain traces these rays back to where it thinks an image is. This results in a virtual image at a shallower depth than is the actual case.
References
1. Refraction of Light by Rick Reed http://www.ps.missouri.edu/rickspage/refract/refraction.html
2. Explore your world with Science Discovery 2 Textbook
3. Answers.Com http://www.answers.com/topic/refractive-index?cat=technology
4. http://www.asiatravel.com/turkey/istanbul/marinprincesskumburgaz/gifs/pool2.jpg
5. http://pachome2.pacific.net.sg/~ezzychan/refraction.htm
Colours of Light by 2E1 Edgar Wong
How are colors produced?
Colors are produced when a light source hits a prism, which separates the white light into its separate colors are called dispersion.
How to get rainbow colors and to recombine the colors again?
Place a second prism positioned in a way that each other’s points are facing away from each other. Shine the light through both prisms.
What are primary colors?
The three primary colors are the minimum number of colors that can be mixed to make the greatest number of other colors. The primary colors cannot be made by mixing other colors.
Effects of mixing of colors.
When you mix colors together, you will get a different color. If you mix the three primary colors together, you get white.
What do you learn about that particular topic?
I’ve learn about the dispersion of white light by a prism and more about the primary colors.
Summarize the key points of that topic.
Colors, they are produced by white light hitting prisms, when lights separates its called dispersion. Placing two prisms facing away from each other can get and recombine colors. When mixing colors together, you get a different color.
Anything interesting to add?
The spectrum consists of: Red, Orange, Blue, Yellow, Green, Indigo and Violet.
Prisms separate the colors already present in the white light.
Credits.
Science Discovery, Rex M Heyworth, 128, 129 and 130, chapter 8
Color Mixing, Robert Truscio.
Colors are produced when a light source hits a prism, which separates the white light into its separate colors are called dispersion.
How to get rainbow colors and to recombine the colors again?
Place a second prism positioned in a way that each other’s points are facing away from each other. Shine the light through both prisms.
What are primary colors?
The three primary colors are the minimum number of colors that can be mixed to make the greatest number of other colors. The primary colors cannot be made by mixing other colors.
Effects of mixing of colors.
When you mix colors together, you will get a different color. If you mix the three primary colors together, you get white.
What do you learn about that particular topic?
I’ve learn about the dispersion of white light by a prism and more about the primary colors.
Summarize the key points of that topic.
Colors, they are produced by white light hitting prisms, when lights separates its called dispersion. Placing two prisms facing away from each other can get and recombine colors. When mixing colors together, you get a different color.
Anything interesting to add?
The spectrum consists of: Red, Orange, Blue, Yellow, Green, Indigo and Violet.
Prisms separate the colors already present in the white light.
Credits.
Science Discovery, Rex M Heyworth, 128, 129 and 130, chapter 8
Color Mixing, Robert Truscio.
Colours of Light by 2E1 Marcus Choo
Colour :
I have learnt that white light, ( ordinary light ), is a mixture of different colours. When a beam of white light passes through a glass prism, the light splits into seven different colours : Red, Orange, Yellow, Green, Blue, Indigo, Violet. We can get white light back again by combining the colours back together. By using a second prism, or by spinning a colour wheel.
We can see the colours of the spectrum, so it is called the visible spectrum. Some people think the there are only six colours as indigo cannot be easily distinguished from blue and violet.
There are three sections : primary colours, secondary colours and teitary colour. Primary colours consist of : Red, Blue and Green.
Secondary colours consist of : Yellow, Cyan and Magenta.
While teitary colour consist of only : White.
A colour filter is a clear plastic or glass that only lets some colours pass through and absorbs the others.
When white light shines on a colours object, some of the colours in the spectrum are reflected and some are absorbed. We see the colour of the reflected light. The colour of an object is the colour of the light that is reflected from it into our eyes.
When the eye detects light, an image is formed on the retina, ( the back of the eye ). The retina has two kinds of light sensitive cells, they are called the rods and the cones. These cells are connected to a nerve which carries signals to the brain, the brain than interprets the signals as light. The rods do not detect colour, they are sensitive to black and white, and work best in dim light. The cones however, detect colour and work best in bright light.
There are tree types of cone cells, one detects red light, another detects blue light and the other detects green light. This means that these cone cells can detect the three primary colours. When white light shines into the eye, all three types of cones respond. For example the cones which detect red light respond to the red light in the white light and the brain receives signals from all these types of cones and interprets them as white light.
I have learnt that white light, ( ordinary light ), is a mixture of different colours. When a beam of white light passes through a glass prism, the light splits into seven different colours : Red, Orange, Yellow, Green, Blue, Indigo, Violet. We can get white light back again by combining the colours back together. By using a second prism, or by spinning a colour wheel.
We can see the colours of the spectrum, so it is called the visible spectrum. Some people think the there are only six colours as indigo cannot be easily distinguished from blue and violet.
There are three sections : primary colours, secondary colours and teitary colour. Primary colours consist of : Red, Blue and Green.
Secondary colours consist of : Yellow, Cyan and Magenta.
While teitary colour consist of only : White.
A colour filter is a clear plastic or glass that only lets some colours pass through and absorbs the others.
When white light shines on a colours object, some of the colours in the spectrum are reflected and some are absorbed. We see the colour of the reflected light. The colour of an object is the colour of the light that is reflected from it into our eyes.
When the eye detects light, an image is formed on the retina, ( the back of the eye ). The retina has two kinds of light sensitive cells, they are called the rods and the cones. These cells are connected to a nerve which carries signals to the brain, the brain than interprets the signals as light. The rods do not detect colour, they are sensitive to black and white, and work best in dim light. The cones however, detect colour and work best in bright light.
There are tree types of cone cells, one detects red light, another detects blue light and the other detects green light. This means that these cone cells can detect the three primary colours. When white light shines into the eye, all three types of cones respond. For example the cones which detect red light respond to the red light in the white light and the brain receives signals from all these types of cones and interprets them as white light.
Reflection of Light by 2E3 Siti Saiyidah Nafisah
I have learnt that reflection is the bouncing of light off a mirror. A plane mirror is a good reflector of light.
When a ray of light strikes the mirror at a right angle, it is reflected along the same path, called the normal. When a ray of light hits a plane mirror at an angle to the normal (called the angle of incidence), it is reflected at an equal angle but on the opposite side of the normal (angle of reflection). These two angles are always equal no matter how light rays strike the mirror. These are called The Law of Reflection.
In a plane mirror, the image is upright and of the same size as the object. In a plane mirror, the image lies as far behind the mirror as the object is in front of the mirror. Mirrors turn images around from left to right. Hence, in a plane mirror, an image is laterally inverted. An image that cannot be formed on a screen is called a virtual image. In a plane mirror, the image formed is always a virtual image.
There are two types of reflection- Regular reflection and Diffuse reflection.
Textbook Resource: Science Txtbk (pg119-121)
When a ray of light strikes the mirror at a right angle, it is reflected along the same path, called the normal. When a ray of light hits a plane mirror at an angle to the normal (called the angle of incidence), it is reflected at an equal angle but on the opposite side of the normal (angle of reflection). These two angles are always equal no matter how light rays strike the mirror. These are called The Law of Reflection.
In a plane mirror, the image is upright and of the same size as the object. In a plane mirror, the image lies as far behind the mirror as the object is in front of the mirror. Mirrors turn images around from left to right. Hence, in a plane mirror, an image is laterally inverted. An image that cannot be formed on a screen is called a virtual image. In a plane mirror, the image formed is always a virtual image.
There are two types of reflection- Regular reflection and Diffuse reflection.
Textbook Resource: Science Txtbk (pg119-121)
Refraction of Light by 2E1 Jeong Seok Young
In this physics holiday homework about refraction I have learnt that refraction is happening around us everyday. Example we go to our swimming pool or a bath tub and see the floors of these things are actually closer to us then it actually is.
It is also useful as we could look into fish tanks and see the fishes closer to us giving us a better view. REFER TO PICTURE BELOW
But there are disadvantages like changing the direction of the light and speed of light in different substances.
Now Im going to summarise the key points of the topic REFRACTION
-What is refraction of light?
Refraction is the bending of a wave when it enters a medium where it's speed is different.
-When does it happen? how and when will the light bend?
Refraction happens when light waves travel from a medium with a given refractive index to a medium with another. Light travels inward when entering medium of higher index of refraction.
In the other hand,light travels outward when entering medium of lower index of refraction.
-What is refractive index?
The refractive index also called index of refraction,of a medium is a measure for how much the speed of light is reduced inside the medium.
Effects of refraction?
Effects of refraction happens everyday around us. for example when we see the floors of the swimming pool, it seems closer to us but its actually further away. And when there is a straw inside the cup it should be straight but we see it as bent.
-Anything intresting to add?
What is interesting about refraction is that the lights speed of refraction differs in all different types of substances.
It is also interesting that our eyes see things closer towards us when it is not.
REFRENCES
WEBSITES:
-http://hyperphysics.phy-astr.gsu.edu/Hbase/geoopt/refr.html
-http://www.ps.missouri.edu/rickspage/refract/refraction.html
-http://sol.sci.uop.edu/~jfalward/refraction/refraction.html
-http://micro.magnet.fsu.edu/primer/java/scienceopticsu/refraction/index.html
-http://www.fishnfriends.com/pix/showtank.jpg
ALL SEARCHINGS FROM GOOGLE.COM
It is also useful as we could look into fish tanks and see the fishes closer to us giving us a better view. REFER TO PICTURE BELOW
But there are disadvantages like changing the direction of the light and speed of light in different substances.
Now Im going to summarise the key points of the topic REFRACTION
-What is refraction of light?
Refraction is the bending of a wave when it enters a medium where it's speed is different.
-When does it happen? how and when will the light bend?
Refraction happens when light waves travel from a medium with a given refractive index to a medium with another. Light travels inward when entering medium of higher index of refraction.
In the other hand,light travels outward when entering medium of lower index of refraction.
-What is refractive index?
The refractive index also called index of refraction,of a medium is a measure for how much the speed of light is reduced inside the medium.
Effects of refraction?
Effects of refraction happens everyday around us. for example when we see the floors of the swimming pool, it seems closer to us but its actually further away. And when there is a straw inside the cup it should be straight but we see it as bent.
-Anything intresting to add?
What is interesting about refraction is that the lights speed of refraction differs in all different types of substances.
It is also interesting that our eyes see things closer towards us when it is not.
REFRENCES
WEBSITES:
-http://hyperphysics.phy-astr.gsu.edu/Hbase/geoopt/refr.html
-http://www.ps.missouri.edu/rickspage/refract/refraction.html
-http://sol.sci.uop.edu/~jfalward/refraction/refraction.html
-http://micro.magnet.fsu.edu/primer/java/scienceopticsu/refraction/index.html
-http://www.fishnfriends.com/pix/showtank.jpg
ALL SEARCHINGS FROM GOOGLE.COM
Colours of Light by 2E3 Nur Hasyimah
I’ve learned more about colours, such as the three primary colours, the secondary colours, and lastly, the rainbow. I find that learning about rainbows is the most interesting part of this topic.
Colour is a part of the human vision system. Colours derive from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors. Dispersion of light is the separation of splitting of white light into its separate colours.
The three primary colours are red, blue, and green. Primary colours are sets of colours that can be combined to make a useful range of colours. Mixing of pigments or dyes, such as in printing, the primaries normally used are magenta, cyan and yellow. A secondary colour is a colour made by mixing two primary colours in a given colour space. For example, yellow is a secondary colour because when you mix red and green, you will get yellow.
Rainbows cause a spectrum of light to appear in the sky when the sun shines onto droplets of moisture in the earth’s atmosphere. Rainbows consist of both the primary and the secondary colours. There are seven colours in a rainbow.
There are red, orange, yellow, green, blue, indigo and violet. Rainbows can also be caused by other forms of water than rain, including mist, spray, dew, fog and ice. Rainbows can have shapes other than a bow, including stripes, circles, or even flames. Rainbows can be seen whenever there are water drops in the air and sunlight shining from behind a person on the ground. They are commonly seen near waterfalls or fountains.
Resources:
http://en.wikipedia.org/wiki/Rainbows
http://en.wikipedia.org/wiki/Primary_colours
http://en.wikipedia.org/wiki/Secondary_colours
http://en.wikipedia.org/wiki/Colours
Colour is a part of the human vision system. Colours derive from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors. Dispersion of light is the separation of splitting of white light into its separate colours.
The three primary colours are red, blue, and green. Primary colours are sets of colours that can be combined to make a useful range of colours. Mixing of pigments or dyes, such as in printing, the primaries normally used are magenta, cyan and yellow. A secondary colour is a colour made by mixing two primary colours in a given colour space. For example, yellow is a secondary colour because when you mix red and green, you will get yellow.
Rainbows cause a spectrum of light to appear in the sky when the sun shines onto droplets of moisture in the earth’s atmosphere. Rainbows consist of both the primary and the secondary colours. There are seven colours in a rainbow.
There are red, orange, yellow, green, blue, indigo and violet. Rainbows can also be caused by other forms of water than rain, including mist, spray, dew, fog and ice. Rainbows can have shapes other than a bow, including stripes, circles, or even flames. Rainbows can be seen whenever there are water drops in the air and sunlight shining from behind a person on the ground. They are commonly seen near waterfalls or fountains.
Resources:
http://en.wikipedia.org/wiki/Rainbows
http://en.wikipedia.org/wiki/Primary_colours
http://en.wikipedia.org/wiki/Secondary_colours
http://en.wikipedia.org/wiki/Colours
Colours of light by 2E3 Neo Chin Yen
In this topic, I get to learn the combination and recombination of rainbow colours, and how the colours are being produced, and the effects of mixing all primary colours. I also learnt that colour is a function of the human visual system, and is not an intrinsic property.
Objects don't "have" color, they give off light that "appears" to be a color. Spectral power distributions exist in the physical world, but color exists only in the mind of the beholder.
Color is the perceptual quality of light.
The color of the light coming from an object has its origin in one or more of the following processes …
emission: the object itself is a source of light with a color determined by its spectra
reflection: certain frequencies are reflected from the object while others are not
transmission: certain frequencies are transmitted through the object while others are not
interference: certain frequencies are amplified by constructive interference while others are attenuated by destructive interference
dispersion: the angular separation of a polychromatic light wave by frequency during refraction
scattering: the preferential reradiation of certain frequencies of light striking small, dispersed particles
Something interesting I want to share are some historical junks.
The painter's color wheel is a historical artifact that refuses to die. The primary colors are not red, yellow, and blue. Painters and art teachers promote this scheme. It is a convenient way to understand how to mimic one color by mixing red, yellow, and blue. But these colors do not satisfy the definition of primary colors in that they can't reproduce the widest variety of colors when combined.
Cyan, magenta, and yellow have a greater chromatic range as evidenced by their ability to produce a reasonable black. No combination of red, yellow, and blue pigments will approach black as closely as do cyan, magenta, and yellow.
The website I got all my informations are from www.hypertextbook.com/physics/
Objects don't "have" color, they give off light that "appears" to be a color. Spectral power distributions exist in the physical world, but color exists only in the mind of the beholder.
Color is the perceptual quality of light.
The color of the light coming from an object has its origin in one or more of the following processes …
emission: the object itself is a source of light with a color determined by its spectra
reflection: certain frequencies are reflected from the object while others are not
transmission: certain frequencies are transmitted through the object while others are not
interference: certain frequencies are amplified by constructive interference while others are attenuated by destructive interference
dispersion: the angular separation of a polychromatic light wave by frequency during refraction
scattering: the preferential reradiation of certain frequencies of light striking small, dispersed particles
Something interesting I want to share are some historical junks.
The painter's color wheel is a historical artifact that refuses to die. The primary colors are not red, yellow, and blue. Painters and art teachers promote this scheme. It is a convenient way to understand how to mimic one color by mixing red, yellow, and blue. But these colors do not satisfy the definition of primary colors in that they can't reproduce the widest variety of colors when combined.
Cyan, magenta, and yellow have a greater chromatic range as evidenced by their ability to produce a reasonable black. No combination of red, yellow, and blue pigments will approach black as closely as do cyan, magenta, and yellow.
The website I got all my informations are from www.hypertextbook.com/physics/
Sound by 2E1 Ebel
SOUND
[A]Sound is a form of energy and is caused by objects vibrating .
[B]Sound travels through air as vibrations .When a loudspeaker produce a sound , the vibration of the skin of the speaker causes the surrounding air molecules to also vibrate . These vibration spread outwards , passing on the sound energy until it reaches the ears.
[C]Sound takes time to travel from one place to the other. Sound travels at a speed of 330m/s in air .This is much slower than the speed of light [300 000 000m/s]Thats why you will always see the flash of lighting followed by the crack of thunder .
[D]Sound cannot travel through a vacuum[empty space] it needs a medium[substance] to travel through .Sound can travel through gases , liquid and solids. It travels through liquid and solids faster than gases as the particles of solid and liquids are closer , so the vibration pass more easily .However , the energy of the sound is soon used up passing through liquids and solids .
[E]Sound are all around us and provide a means of communication [talking , whistling and singing ] give us warning signals [alarms , telephones , fire bells , police sirens] give us pleasure [music , singing ]
[F]However some sound are unnecessary , they are describes as noise [ traffic noise , loud music , aircraft noise , building sites noise , drilling noise ]. Sound levels are measured as decibels[dB].The loudest sound , which causes pain is called the threshold of pain.
[G]The ear is the natural detector of sound . The external ear is like a funnel to channel the sound waves towards the ear drum .This then starts to vibrate and the bones in the middle ear amplify this vibration which causes waves in the liquid inside the inner ear. These waves produce electrical pulses in the nerve cells which are carried by the auditory nerve to the brain intercepts these electrical signs as sounds
Biobliography:Science Keynotes -Christopher N. Prescott
[A]Sound is a form of energy and is caused by objects vibrating .
[B]Sound travels through air as vibrations .When a loudspeaker produce a sound , the vibration of the skin of the speaker causes the surrounding air molecules to also vibrate . These vibration spread outwards , passing on the sound energy until it reaches the ears.
[C]Sound takes time to travel from one place to the other. Sound travels at a speed of 330m/s in air .This is much slower than the speed of light [300 000 000m/s]Thats why you will always see the flash of lighting followed by the crack of thunder .
[D]Sound cannot travel through a vacuum[empty space] it needs a medium[substance] to travel through .Sound can travel through gases , liquid and solids. It travels through liquid and solids faster than gases as the particles of solid and liquids are closer , so the vibration pass more easily .However , the energy of the sound is soon used up passing through liquids and solids .
[E]Sound are all around us and provide a means of communication [talking , whistling and singing ] give us warning signals [alarms , telephones , fire bells , police sirens] give us pleasure [music , singing ]
[F]However some sound are unnecessary , they are describes as noise [ traffic noise , loud music , aircraft noise , building sites noise , drilling noise ]. Sound levels are measured as decibels[dB].The loudest sound , which causes pain is called the threshold of pain.
[G]The ear is the natural detector of sound . The external ear is like a funnel to channel the sound waves towards the ear drum .This then starts to vibrate and the bones in the middle ear amplify this vibration which causes waves in the liquid inside the inner ear. These waves produce electrical pulses in the nerve cells which are carried by the auditory nerve to the brain intercepts these electrical signs as sounds
Biobliography:Science Keynotes -Christopher N. Prescott
Refraction of Light by 2E4 Sudha
I learnt : when the light moves from air to glass,it is refracted towards the normal & when the light moves from glass to air,it is refracted away from the normal.
And also that light from an object bends as it comes out of water ; but our brain thinks the light has moved in a straight line. So, the object appears to be at a higher position than it actually is.
the key points :
Light is bent or refracted when it passes from one transparent material into another,such as from air to glass and vice versa.
Two effects of refraction are (a)an object in water appears nearer to the surface than it really is and (b)an object such as a stick placed in water appears to be bent.
Refraction is the change in direction of a wave due to a change in its speed. This is most commonly seen when a wave passes from one medium to another.
In optics, refraction occurs when light waves travel from a medium with a given refractive index to a medium with another. At the boundary between the media, the wave's phase velocity is altered, it changes direction, and its wavelength increases or decreases but its frequency remains constant.
For example, a light ray will refract as it enters and leaves glass; understanding of this concept led to the invention of lenses and the refracting telescope.
And also that light from an object bends as it comes out of water ; but our brain thinks the light has moved in a straight line. So, the object appears to be at a higher position than it actually is.
the key points :
Light is bent or refracted when it passes from one transparent material into another,such as from air to glass and vice versa.
Two effects of refraction are (a)an object in water appears nearer to the surface than it really is and (b)an object such as a stick placed in water appears to be bent.
Refraction is the change in direction of a wave due to a change in its speed. This is most commonly seen when a wave passes from one medium to another.
In optics, refraction occurs when light waves travel from a medium with a given refractive index to a medium with another. At the boundary between the media, the wave's phase velocity is altered, it changes direction, and its wavelength increases or decreases but its frequency remains constant.
For example, a light ray will refract as it enters and leaves glass; understanding of this concept led to the invention of lenses and the refracting telescope.
Refraction of Light by 2E4 Shamani Rachel
I learnt from this particular topic that,when the light moves from air to glass,it is refracted towards the normal & when the light moves from glass to air,it is refracted away from the normal.
And also that light from an object bends as it comes out of water ; but our brain thinks the light has moved in a straight line. So, the object appears to be at a higher position than it actually is.
& to summarise the key points :
Light is bent or refracted when it passes from one transparent material into another,such as from air to glass and vice versa.
Two effects of refraction are (a)an object in water appears nearer to the surface than it really is and (b)an object such as a stick placed in water appears to be bent.
Refraction is responsible for image formation by lenses and the eye.
The Snell's Law :D
In 1621, a Dutch physicist named Willebrord Snell (1591-1626), derived the relationship between the different angles of light as it passes from one transperent medium to another.
When light passes from one transparent medium to another, it bends according to Snell's law which states:
Ni * Sin(Ai) = Nr * Sin(Ar),
where: Ni is the refractive index of the medium the light is leaving, Ai is the incident angle between the light ray and the normal to the meduim to medium interface, Nr is the refractive index of the medium the light is entering, Ar is the refractive angle between the light ray and the normal to the meduim to medium interface.
*Information taken from,
www.google.com.sg :
http://www.ps.missouri.edu/rickspage/refract/refraction.html
http://hyperphysics.phy-astr.gsu.edu/Hbase/geoopt/refr.html
& the science textbook.
And also that light from an object bends as it comes out of water ; but our brain thinks the light has moved in a straight line. So, the object appears to be at a higher position than it actually is.
& to summarise the key points :
Light is bent or refracted when it passes from one transparent material into another,such as from air to glass and vice versa.
Two effects of refraction are (a)an object in water appears nearer to the surface than it really is and (b)an object such as a stick placed in water appears to be bent.
Refraction is responsible for image formation by lenses and the eye.
The Snell's Law :D
In 1621, a Dutch physicist named Willebrord Snell (1591-1626), derived the relationship between the different angles of light as it passes from one transperent medium to another.
When light passes from one transparent medium to another, it bends according to Snell's law which states:
Ni * Sin(Ai) = Nr * Sin(Ar),
where: Ni is the refractive index of the medium the light is leaving, Ai is the incident angle between the light ray and the normal to the meduim to medium interface, Nr is the refractive index of the medium the light is entering, Ar is the refractive angle between the light ray and the normal to the meduim to medium interface.
*Information taken from,
www.google.com.sg :
http://www.ps.missouri.edu/rickspage/refract/refraction.html
http://hyperphysics.phy-astr.gsu.edu/Hbase/geoopt/refr.html
& the science textbook.
Sound by 2E4 Luan Niannian
What is sound?
Soundis a from of energy.It is caused by vibrations.Sound is the quickly varying pressure wave within a medium. We usually mean audible sound, which is the sensation (as detected by the ear) of very small rapid changes in the air pressure above and below a static value. This "static" value is atmospheric pressure (about 100,000 Pascals) which does nevertheless vary slowly, as shown on a barometer. Associated with the sound pressure wave is a flow of energy.
Sound is often represented diagrammatically as a sine wave, but physically sound (in air) is a longitudinal wave where the wave motion is in the direction of the movement of energy. The wave crests can be considered as the pressure maxima whilst the troughs represent the pressure minima.
How small and rapid are the changes of air pressure which cause sound?
When the rapid variations in pressure occur between about 20 and 20,000 times per second (i.e. at a frequency between 20Hz and 20kHz) sound is potentially audible even though the pressure variation can sometimes be as low as only a few tens of millionths of a Pascal. Movements of the ear drum as small as the diameter of a hydrogen atom can be audible!
Louder sounds are caused by greater variation in pressure. A sound wave of one Pascal amplitude, for example, will sound quite loud, provided that most of the acoustic energy is in the mid-frequencies (1kHz - 4kHz) where the human ear is most sensitive. It is commonly accepted that the threshold of human hearing for a 1 kHz sound wave is about 20 micro-Pascals.
What makes sound?
Sound is produced when the air is disturbed in some way, for example by a vibrating object. A speaker cone from a high fidelity system serves as a good illustration. It may be possible to see the movement of a bass speaker cone, providing it is producing very low frequency sound. As the cone moves forward the air immediately in front is compressed causing a slight increase in air pressure, it then moves back past its rest position and causes a reduction in the air pressure (rarefaction). The process continues so that a wave of alternating high and low pressure is radiated away from the speaker cone at the speed of sound.
What affects sound?
Sound can travel through solids,liquids and gases.Sound cannot travel through vacuum because it requires a medium to travel. Voices in different substances in different speed. The speed of sound effects spread to two factors: media and wave source The surrounding temperature changes, the density of the air has changed (the higher the temperature, density greater, because the higher the temperature, air Lengsu heat up, so will have partial pressure increases, that is, increasing density) is the medium change The The voice of the spread of medium density greater voice transmission of the greater speed That is, the higher the temperature in the voice of the environment in the faster spread
What is a decibel (dB)?
The decibel is a logarithmic unit which is used in a number of scientific disciplines. Other examples are the Richter scale for earthquake event energy and pH for hydrogen ion concentration in liquids.
In all cases the logarithmic measure is used to compare the quantity of interest with a reference value, often the smallest likely value of the quantity. Sometimes it can be an approximate average value.
In acoustics the decibel is most often used to compare sound pressure, in air, with a reference pressure. References for sound intensity, sound power and sound pressure in water are amongst others which are also commonly in use.
How is sound measured?
A sound level meter is the principal instrument for general noise measurement. The indication on a sound level meter (aside from weighting considerations) indicates the sound pressure, p, as a level referenced to 0.00002 Pa, calibrated on a decibel scale.
http://www.tek-ltd.com/school2.htm
Soundis a from of energy.It is caused by vibrations.Sound is the quickly varying pressure wave within a medium. We usually mean audible sound, which is the sensation (as detected by the ear) of very small rapid changes in the air pressure above and below a static value. This "static" value is atmospheric pressure (about 100,000 Pascals) which does nevertheless vary slowly, as shown on a barometer. Associated with the sound pressure wave is a flow of energy.
Sound is often represented diagrammatically as a sine wave, but physically sound (in air) is a longitudinal wave where the wave motion is in the direction of the movement of energy. The wave crests can be considered as the pressure maxima whilst the troughs represent the pressure minima.
How small and rapid are the changes of air pressure which cause sound?
When the rapid variations in pressure occur between about 20 and 20,000 times per second (i.e. at a frequency between 20Hz and 20kHz) sound is potentially audible even though the pressure variation can sometimes be as low as only a few tens of millionths of a Pascal. Movements of the ear drum as small as the diameter of a hydrogen atom can be audible!
Louder sounds are caused by greater variation in pressure. A sound wave of one Pascal amplitude, for example, will sound quite loud, provided that most of the acoustic energy is in the mid-frequencies (1kHz - 4kHz) where the human ear is most sensitive. It is commonly accepted that the threshold of human hearing for a 1 kHz sound wave is about 20 micro-Pascals.
What makes sound?
Sound is produced when the air is disturbed in some way, for example by a vibrating object. A speaker cone from a high fidelity system serves as a good illustration. It may be possible to see the movement of a bass speaker cone, providing it is producing very low frequency sound. As the cone moves forward the air immediately in front is compressed causing a slight increase in air pressure, it then moves back past its rest position and causes a reduction in the air pressure (rarefaction). The process continues so that a wave of alternating high and low pressure is radiated away from the speaker cone at the speed of sound.
What affects sound?
Sound can travel through solids,liquids and gases.Sound cannot travel through vacuum because it requires a medium to travel. Voices in different substances in different speed. The speed of sound effects spread to two factors: media and wave source The surrounding temperature changes, the density of the air has changed (the higher the temperature, density greater, because the higher the temperature, air Lengsu heat up, so will have partial pressure increases, that is, increasing density) is the medium change The The voice of the spread of medium density greater voice transmission of the greater speed That is, the higher the temperature in the voice of the environment in the faster spread
What is a decibel (dB)?
The decibel is a logarithmic unit which is used in a number of scientific disciplines. Other examples are the Richter scale for earthquake event energy and pH for hydrogen ion concentration in liquids.
In all cases the logarithmic measure is used to compare the quantity of interest with a reference value, often the smallest likely value of the quantity. Sometimes it can be an approximate average value.
In acoustics the decibel is most often used to compare sound pressure, in air, with a reference pressure. References for sound intensity, sound power and sound pressure in water are amongst others which are also commonly in use.
How is sound measured?
A sound level meter is the principal instrument for general noise measurement. The indication on a sound level meter (aside from weighting considerations) indicates the sound pressure, p, as a level referenced to 0.00002 Pa, calibrated on a decibel scale.
http://www.tek-ltd.com/school2.htm
Electricity by 2E1 Chen Meng
What is electricity?
It is a controllable and convenient form of energy,
evident from the fact that it runs machinery and can
be transformed into other types of energy such as
light and heat.
It is invisible. During an electrical
storm, we do not see electricity.
We observe the air being ionized when
the electricity travels through it.
Sources of electricity
Electrical energy comes from two main sources. There are mains electricity and electric cells.
Main electricity is generated in power stations. The plugs of electrical appliances are inserted into mains sockets to obtain this electricity. Mains electricity supplies a lot of energy. It can give us an electric shock which can kill us. Never touch bare wires connected to mains electricity.
Electric cells give out only a little energy. They are used in many portable electrical devices and are safe to use.
Types of electricity
Static electricity is electricity that says still on objects.
Current electricity is electricity that flows in an electric circuit.
Electric circuits
To make an electrical appliance work, electricity must flow through it. The flow of electricity is called an electric current.
The path along which the electric current moves is called the electric circuit.
In the laboratory, experiments with electricity are often done on a circuit board.
On the circuit board, we join up electrical components to make a circuit.
Closed circuit & open circuits
For the bulb to light up, there has to be a complete path without any gap from one end of the cell to the light bulb and back to the other end of the cell. This complete path is called a closed circuit.
Each circuit has a gap in it and the bulbs do not light up. Incomplete circuits are called open circuits.
An electric current flow only when there is a source of electrical energy and a closed circuit.
Cell
Supplies electrical energy.The larger terminal (on the left) is positive (+). A single cell is often called a battery, but strictly a battery is two or more cells joined together.
Battery
Supplies electrical energy. A battery is more than one cell.The larger terminal (on the left) is positive (+).
Output Devices: Lamps, Heater, Motor, etc.
Component
Circuit Symbol
Function of Component
Lamp (lighting)
A transducer which converts electrical energy to light. This symbol is used for a lamp providing illumination, for example a car headlamp or torch bulb.
Lamp (indicator)
A transducer which converts electrical energy to light. This symbol is used for a lamp which is an indicator.
Heater
A transducer which converts electrical energy to heat.
Motor
A transducer which converts electrical energy to kinetic energy (motion).
Bell
A transducer which converts electrical energy to sound.
Buzzer
A transducer which converts electrical energy to sound.
Push Switch(push-to-make)
A push switch allows current to flow only when the button is pressed. This is the switch used to operate a doorbell.
Push-to-Break Switch
This type of push switch is normally closed (on), it is open (off) only when the button is pressed.
On-Off Switch(SPST)
SPST = Single Pole, Single Throw.An on-off switch allows current to flow only when it is in the closed (on) position.
Resistor
A resistor restricts the flow of current, for example to limit the current passing through an LED. A resistor is used with a capacitor in a timing circuit. Some publications still use the old resistor symbol:
Variable Resistor(Rheostat)
This type of variable resistor with 2 contacts (a rheostat) is usually used to control current. Examples include: adjusting lamp brightness, adjusting motor speed, and adjusting the rate of flow of charge into a capacitor in a timing circuit.
Voltmeter
A voltmeter is used to measure voltage. The proper name for voltage is 'potential difference', but most people prefer to say voltage!
Ammeter
An ammeter is used to measure current.
Ohmmeter
An ohmmeter is used to measure resistance. Most multimeters have an ohmmeter setting.
Switches
A switch is used to open or close a circuit.
Conductors & Insulators
Allows electricity to pass through it is called an electrical conductor.
A material which does not allow electricity to pass through it is called an electrical insulator.
What is voltage?
Voltage is a measure of how much energy the electrons receive. To measure voltage we use a voltmeter.
The SI unit for voltage is the volt (V).
Series circuits & parallel circuits
Electric circuits can be classified into two main types----series circuits and parallel circuits.
In a series circuits, each component is joined to the next to form a single path. The current that flows through each of the components is the same. However, a break in any part of a series circuit stops the flow of current in the whole circuit.
☆ the current at different points of the electric circuit is the same.
☆ the voltage of the energy source is the sum of the voltage of all the batteries in series.
☆ the total voltage across the whole circuit is the sum of the voltage of all the batteries in series.
A parallel circuit divides into two or more branches with electrical components in each branch. The current divides and flows through each of the three branches. An advantage of this circuit is that if one bulb breaks or is removed, the other bulbs remain lit.
☆ the current is the sum of all the current in the braches of a parallel circuit.
☆ the voltage across each branch is the same.
☆ the total voltage of cells/batteries connected on parallel is the voltage of one cell/battery.
What is an Electric Current?
An electric current is the flow of electrons in one direction in a circuit.
How does electricity travel in circuits?
Electricity travels in closed circuits. It must have a complete path before the electrons can move. If a circuit is open, the electrons cannot flow. When we flip on a light switch, we close a circuit. The electricity flows from the electric wire through the light and back into the wire. When we flip the switch off, we open the circuit. No electricity flows to the light. Electricity flows through a tiny wire in the bulb when we turn a light switch on. The wire gets very hot. It makes the gas in the bulb glow. When the bulb burns out, the tiny wire has broken. The path through the bulb is gone.
Measuring electric current
An ammeter is used to measure the electric current.
The SI unit for electric current is the ampere (A). Smaller currents can be measured in milliamperes (mA)
1A=1000mA
1mA=1/1000A
What is resistor?
An electricity component that is specially made to have a certain resistance is called a resistor.
Resistors that have one fixed resistance are called fixed resistors.
We used rheostat to change the current in a circuit. (rheostat which is also called a variable resistor.)
Resistance = voltage across component /
Current though component
Effects of an electric current
The flow of an electric current produces three effects.
☆ HEATING effect
☆ CHEMICAL effect
☆ MAGNETIC effect
The above sources are taken from website and sec. 2 textbook.
http://www.eia.doe.gov/kids/energyfacts/sources/electricity.html
http://www.sciencetech.technomuses.ca/english/schoolzone/Info_Electricity.cfm#whatis
http://people.virginia.edu/~bwk7j/basic.htm
http://www.kpsec.freeuk.com/symbol.htm
It is a controllable and convenient form of energy,
evident from the fact that it runs machinery and can
be transformed into other types of energy such as
light and heat.
It is invisible. During an electrical
storm, we do not see electricity.
We observe the air being ionized when
the electricity travels through it.
Sources of electricity
Electrical energy comes from two main sources. There are mains electricity and electric cells.
Main electricity is generated in power stations. The plugs of electrical appliances are inserted into mains sockets to obtain this electricity. Mains electricity supplies a lot of energy. It can give us an electric shock which can kill us. Never touch bare wires connected to mains electricity.
Electric cells give out only a little energy. They are used in many portable electrical devices and are safe to use.
Types of electricity
Static electricity is electricity that says still on objects.
Current electricity is electricity that flows in an electric circuit.
Electric circuits
To make an electrical appliance work, electricity must flow through it. The flow of electricity is called an electric current.
The path along which the electric current moves is called the electric circuit.
In the laboratory, experiments with electricity are often done on a circuit board.
On the circuit board, we join up electrical components to make a circuit.
Closed circuit & open circuits
For the bulb to light up, there has to be a complete path without any gap from one end of the cell to the light bulb and back to the other end of the cell. This complete path is called a closed circuit.
Each circuit has a gap in it and the bulbs do not light up. Incomplete circuits are called open circuits.
An electric current flow only when there is a source of electrical energy and a closed circuit.
Cell
Supplies electrical energy.The larger terminal (on the left) is positive (+). A single cell is often called a battery, but strictly a battery is two or more cells joined together.
Battery
Supplies electrical energy. A battery is more than one cell.The larger terminal (on the left) is positive (+).
Output Devices: Lamps, Heater, Motor, etc.
Component
Circuit Symbol
Function of Component
Lamp (lighting)
A transducer which converts electrical energy to light. This symbol is used for a lamp providing illumination, for example a car headlamp or torch bulb.
Lamp (indicator)
A transducer which converts electrical energy to light. This symbol is used for a lamp which is an indicator.
Heater
A transducer which converts electrical energy to heat.
Motor
A transducer which converts electrical energy to kinetic energy (motion).
Bell
A transducer which converts electrical energy to sound.
Buzzer
A transducer which converts electrical energy to sound.
Push Switch(push-to-make)
A push switch allows current to flow only when the button is pressed. This is the switch used to operate a doorbell.
Push-to-Break Switch
This type of push switch is normally closed (on), it is open (off) only when the button is pressed.
On-Off Switch(SPST)
SPST = Single Pole, Single Throw.An on-off switch allows current to flow only when it is in the closed (on) position.
Resistor
A resistor restricts the flow of current, for example to limit the current passing through an LED. A resistor is used with a capacitor in a timing circuit. Some publications still use the old resistor symbol:
Variable Resistor(Rheostat)
This type of variable resistor with 2 contacts (a rheostat) is usually used to control current. Examples include: adjusting lamp brightness, adjusting motor speed, and adjusting the rate of flow of charge into a capacitor in a timing circuit.
Voltmeter
A voltmeter is used to measure voltage. The proper name for voltage is 'potential difference', but most people prefer to say voltage!
Ammeter
An ammeter is used to measure current.
Ohmmeter
An ohmmeter is used to measure resistance. Most multimeters have an ohmmeter setting.
Switches
A switch is used to open or close a circuit.
Conductors & Insulators
Allows electricity to pass through it is called an electrical conductor.
A material which does not allow electricity to pass through it is called an electrical insulator.
What is voltage?
Voltage is a measure of how much energy the electrons receive. To measure voltage we use a voltmeter.
The SI unit for voltage is the volt (V).
Series circuits & parallel circuits
Electric circuits can be classified into two main types----series circuits and parallel circuits.
In a series circuits, each component is joined to the next to form a single path. The current that flows through each of the components is the same. However, a break in any part of a series circuit stops the flow of current in the whole circuit.
☆ the current at different points of the electric circuit is the same.
☆ the voltage of the energy source is the sum of the voltage of all the batteries in series.
☆ the total voltage across the whole circuit is the sum of the voltage of all the batteries in series.
A parallel circuit divides into two or more branches with electrical components in each branch. The current divides and flows through each of the three branches. An advantage of this circuit is that if one bulb breaks or is removed, the other bulbs remain lit.
☆ the current is the sum of all the current in the braches of a parallel circuit.
☆ the voltage across each branch is the same.
☆ the total voltage of cells/batteries connected on parallel is the voltage of one cell/battery.
What is an Electric Current?
An electric current is the flow of electrons in one direction in a circuit.
How does electricity travel in circuits?
Electricity travels in closed circuits. It must have a complete path before the electrons can move. If a circuit is open, the electrons cannot flow. When we flip on a light switch, we close a circuit. The electricity flows from the electric wire through the light and back into the wire. When we flip the switch off, we open the circuit. No electricity flows to the light. Electricity flows through a tiny wire in the bulb when we turn a light switch on. The wire gets very hot. It makes the gas in the bulb glow. When the bulb burns out, the tiny wire has broken. The path through the bulb is gone.
Measuring electric current
An ammeter is used to measure the electric current.
The SI unit for electric current is the ampere (A). Smaller currents can be measured in milliamperes (mA)
1A=1000mA
1mA=1/1000A
What is resistor?
An electricity component that is specially made to have a certain resistance is called a resistor.
Resistors that have one fixed resistance are called fixed resistors.
We used rheostat to change the current in a circuit. (rheostat which is also called a variable resistor.)
Resistance = voltage across component /
Current though component
Effects of an electric current
The flow of an electric current produces three effects.
☆ HEATING effect
☆ CHEMICAL effect
☆ MAGNETIC effect
The above sources are taken from website and sec. 2 textbook.
http://www.eia.doe.gov/kids/energyfacts/sources/electricity.html
http://www.sciencetech.technomuses.ca/english/schoolzone/Info_Electricity.cfm#whatis
http://people.virginia.edu/~bwk7j/basic.htm
http://www.kpsec.freeuk.com/symbol.htm
Reflection of Light by 2E3 Elson Yeo
What is reflection of light?
When you look into a mirror, you see a picture of yourself. What you see is called an image. The image in a mirror is formed when light rays bounce off the mirror and travel to your eyes. This bouncing of light off a mirror is called reflection.
A flat mirror, called a plane mirror, is a good reflector of light. When a ray of light strikes the mirror at a right angle, it is reflected along the same path.
Scientists call this line the normal. When a ray of light hits a plane mirror at an angel to the normal, called the angel of incidence, it is reflected at an equal angle but on the opposite side of the normal, the angel of reflection. These two opposite side of the normal, the angle of reflection. The two angels are always equal no matter how light rays strike the mirror.
This generalization is called the law of reflection.
When does it happen?
When a ray of light hits a surface, it bounces off or reflects and then reaches our eyes. This phenomenon by which a ray of light changes the direction of propagation when it strikes a boundary between different media through which it cannot pass is described as the reflection of light
Types of reflection
There are two types of reflection – regular reflection and diffuse reflection.
When a parallel beam of light hits a smooth surface such as a plane mirror, it is reflected as a parallel beam. This is called regular reflection. An image is formed with regular reflection. That is, when we look at a smooth surface, we can see an image.
Most surfaces are actually quite rough. When a beam of light hits a rough surface, the individual rays are reflected in different directions. So no image is formed. This type of reflection is called diffuse reflection.
Uses of reflection of light and examples?
Convex mirrors are often used in shops as security mirrors because of the type of image produced by that mirror. The image is smaller but shows a wide angle view of the shop.
Concave mirrors are often used in torch lights or in the headlights of cars. The light travels in all directions from the light globe towards the mirror behind it. The rays are then reflected by the mirror and they form a beam of light (a bundle of parallel rays).
http://www.tutorvista.com/content/science/science-ii/reflection-light/reflection-light.php
http://www1.curriculum.edu.au/sciencepd/readings/ligh_reflection.htm
Textbook Page 119 , 121 & 122
When you look into a mirror, you see a picture of yourself. What you see is called an image. The image in a mirror is formed when light rays bounce off the mirror and travel to your eyes. This bouncing of light off a mirror is called reflection.
A flat mirror, called a plane mirror, is a good reflector of light. When a ray of light strikes the mirror at a right angle, it is reflected along the same path.
Scientists call this line the normal. When a ray of light hits a plane mirror at an angel to the normal, called the angel of incidence, it is reflected at an equal angle but on the opposite side of the normal, the angel of reflection. These two opposite side of the normal, the angle of reflection. The two angels are always equal no matter how light rays strike the mirror.
This generalization is called the law of reflection.
When does it happen?
When a ray of light hits a surface, it bounces off or reflects and then reaches our eyes. This phenomenon by which a ray of light changes the direction of propagation when it strikes a boundary between different media through which it cannot pass is described as the reflection of light
Types of reflection
There are two types of reflection – regular reflection and diffuse reflection.
When a parallel beam of light hits a smooth surface such as a plane mirror, it is reflected as a parallel beam. This is called regular reflection. An image is formed with regular reflection. That is, when we look at a smooth surface, we can see an image.
Most surfaces are actually quite rough. When a beam of light hits a rough surface, the individual rays are reflected in different directions. So no image is formed. This type of reflection is called diffuse reflection.
Uses of reflection of light and examples?
Convex mirrors are often used in shops as security mirrors because of the type of image produced by that mirror. The image is smaller but shows a wide angle view of the shop.
Concave mirrors are often used in torch lights or in the headlights of cars. The light travels in all directions from the light globe towards the mirror behind it. The rays are then reflected by the mirror and they form a beam of light (a bundle of parallel rays).
http://www.tutorvista.com/content/science/science-ii/reflection-light/reflection-light.php
http://www1.curriculum.edu.au/sciencepd/readings/ligh_reflection.htm
Textbook Page 119 , 121 & 122
Electricity by 2E3 Joevenn Ng
What Is Electricity?
Electricity is the flow of electrical power or charge. It is a secondary energy source which means that we get it from the conversion of other sources of energy, like coal, natural gas, oil, nuclear power and other natural sources, which are called primary sources. The energy sources we use to make electricity can be renewable or non-renewable, but electricity itself is neither renewable or non-renewable.
Source for this question: http://www.eia.doe.gov/kids/energyfacts/sources/electricity.html
How Is Electricity Produced?
Electricity generation - whether from fossil fuels, nuclear, renewable fuels, or other sources - is usually* based on the fact that "When magnets are moved near a wire, an electric current is generated in that wire."
"When magnets are moved near a wire, an electric current is generated in that wire."
Source for this question: http://hawaii.gov/dbedt/info/energy/renewable/electricitygeneration/
Uses Of Electricity.
Well electricity is widely used all around the world. They are used to do things like using a computer , charging of handphones and others. Electricity is used or all used for good and bad things.
Electricity is the flow of electrical power or charge. It is a secondary energy source which means that we get it from the conversion of other sources of energy, like coal, natural gas, oil, nuclear power and other natural sources, which are called primary sources. The energy sources we use to make electricity can be renewable or non-renewable, but electricity itself is neither renewable or non-renewable.
Source for this question: http://www.eia.doe.gov/kids/energyfacts/sources/electricity.html
How Is Electricity Produced?
Electricity generation - whether from fossil fuels, nuclear, renewable fuels, or other sources - is usually* based on the fact that "When magnets are moved near a wire, an electric current is generated in that wire."
"When magnets are moved near a wire, an electric current is generated in that wire."
Source for this question: http://hawaii.gov/dbedt/info/energy/renewable/electricitygeneration/
Uses Of Electricity.
Well electricity is widely used all around the world. They are used to do things like using a computer , charging of handphones and others. Electricity is used or all used for good and bad things.
Reflection of Light by 2E2 Andre Lim
Topic: Reflection of light – i. What is reflection of light?
ii. When does it happen?
iii. Types of reflection
iv. Uses of reflection of light, examples?
Reflection is the bouncing of light off a mirror or mirror-like surface. Reflection is also the change in direction of a wave front at an interface between two different media so that the wave front returns into the medium from which it originated from.
A flat mirror called a plane mirror is a good reflector of light. A normal is formed when a ray of light strikes the mirror at a right angle.
-Reflection may even occur on water and clouds
Mainly, there are two types of reflection, specular and diffused.Light being reflected of a smooth surface is Specular. When light strikes this smooth surface, all the reflected rays are in line with each other. An image is formed.
Diffused reflection is reflection from a rough surface. The small bumps and irregularities on a rough surface will cause each of the light rays to reflect n different directions, thus no image is formed.
There are some uses of plane mirrors, for example, plane mirrors helps people to check their appearance, and see things at a certain angle which the eye cannot.
The use of curved mirrors is used to reflect light into microscope to amplify the image’s size and dentist can use it to magnify the image of a patient’s teeth.
Also, if you look place a screen behind the mirror, the image is not formed on the screen. An image that cannot be formed on a screen is known as a virtual image.
Acknowledgement: http://en.wikipedia.org/wiki/Reflection_(physics)#Laws_of_regular_reflection
Sec 2 Science Text Book
Pictures - http://en.wikipedia.org/wiki/Image:Crepuscular_Rays_in_ggp_14.jpg
ii. When does it happen?
iii. Types of reflection
iv. Uses of reflection of light, examples?
Reflection is the bouncing of light off a mirror or mirror-like surface. Reflection is also the change in direction of a wave front at an interface between two different media so that the wave front returns into the medium from which it originated from.
A flat mirror called a plane mirror is a good reflector of light. A normal is formed when a ray of light strikes the mirror at a right angle.
-Reflection may even occur on water and clouds
Mainly, there are two types of reflection, specular and diffused.Light being reflected of a smooth surface is Specular. When light strikes this smooth surface, all the reflected rays are in line with each other. An image is formed.
Diffused reflection is reflection from a rough surface. The small bumps and irregularities on a rough surface will cause each of the light rays to reflect n different directions, thus no image is formed.
There are some uses of plane mirrors, for example, plane mirrors helps people to check their appearance, and see things at a certain angle which the eye cannot.
The use of curved mirrors is used to reflect light into microscope to amplify the image’s size and dentist can use it to magnify the image of a patient’s teeth.
Also, if you look place a screen behind the mirror, the image is not formed on the screen. An image that cannot be formed on a screen is known as a virtual image.
Acknowledgement: http://en.wikipedia.org/wiki/Reflection_(physics)#Laws_of_regular_reflection
Sec 2 Science Text Book
Pictures - http://en.wikipedia.org/wiki/Image:Crepuscular_Rays_in_ggp_14.jpg
Electricity by 2E2 Amruth
What is electricity?
*Electricity is a form of energy and it is convenient as it can be changed into other forms of energy.
What are the effects of electricity on our daily lives?
*We are able to; play games on our computer, travel in cars and other transportations, Watch television, use handphones, etc.
What is the electric current?
*It is the flow of electricity.
What is the electrical circuit?
*It is the path where current moves.
What is the meaning of closed circuit and open circuits?
Closed circuit
*It is a complete path of electricity from one end to the other.
Open circuit
*It is an incomplete path of electricity from one end.
Why are switches used in our daily life?
It is safer way to conduct electricity and to open and close circuits.
What is voltage?
*Voltage is the energy per unit charge.
What is the SI unit for voltage?
*The SI unit for voltage is volt ( V ).
Some interesting stuff…….
*In the times when humans first appeared on Earth, the created electricity by rubbing two materials together.
*The first machine to make an electrical spark was created at 1650; it worked by rubbing a hand on a spinning sulphur ball…. Electricity through friction?
RESOURCES
http://www.historyoftheuniverse.com/electric.html
http://en.wikipedia.org/wiki/Voltage
Book: Explore your world with SCIENCE DISCOVERY 2
Publisher: Pearson Longman
Author : Rex M Heyworth
*Electricity is a form of energy and it is convenient as it can be changed into other forms of energy.
What are the effects of electricity on our daily lives?
*We are able to; play games on our computer, travel in cars and other transportations, Watch television, use handphones, etc.
What is the electric current?
*It is the flow of electricity.
What is the electrical circuit?
*It is the path where current moves.
What is the meaning of closed circuit and open circuits?
Closed circuit
*It is a complete path of electricity from one end to the other.
Open circuit
*It is an incomplete path of electricity from one end.
Why are switches used in our daily life?
It is safer way to conduct electricity and to open and close circuits.
What is voltage?
*Voltage is the energy per unit charge.
What is the SI unit for voltage?
*The SI unit for voltage is volt ( V ).
Some interesting stuff…….
*In the times when humans first appeared on Earth, the created electricity by rubbing two materials together.
*The first machine to make an electrical spark was created at 1650; it worked by rubbing a hand on a spinning sulphur ball…. Electricity through friction?
RESOURCES
http://www.historyoftheuniverse.com/electric.html
http://en.wikipedia.org/wiki/Voltage
Book: Explore your world with SCIENCE DISCOVERY 2
Publisher: Pearson Longman
Author : Rex M Heyworth
Electricity by 2E2 Naqiah
Electricity
Electricity is a form of energy produced by the movement of electrons. Electricity is electrical power or an electric current. This form of energy can be sent through wires in a flow of tiny particles. It is used to produce light and heat and to run motors.
Electricity is a basic feature of all matter, of everything in the universe. Electrical force holds atoms and molecules together. Electricity determines the structure of every object that exists. Together with magnetism, it causes a force called electromagnetism, a fundamental force of the universe. Electricity or electrical signals are essential to many biological processes. In our bodies, electrical signals are carried through the nervous system, moving information to and from the brain. Electrical signals communicate to our brain what the eyes see, what the ears hear, and what the fingers feel.
Electrical signals from our brain causes our muscle movements. Electrical signals cause each heartbeat. One of the most important forms of electricity is in electrical current. During the industrial revolution of the 1800s, people began to find ways to use electricity to do work. Today electricity is used throughout our homes, at work, in communication, in transportation, and in medicine and science.
Electrically powered devices are prevalent. Relatively cheap electricity has made electrical appliances, machines, and other devices possible. A major reason electricity works is because of conductors. First metal, water, tall trees and tall items are good conductors because lightning is attracted to them. These materials have many mobile electrons.
Metal is an easy substance for lightning to travel through so metals are good conductors.However, rubber is a bad conductor because lightning bounces off of it. A bad conductor is called an insulator. An insulator has a few mobile electrons. It is important for us to know the difference between good conductors and insulators because if you're outside in an open field during a storm you will know where to go to be safe from the lightning. Truly, knowing the difference between conductors and insulators of electricity can save our lives.
It is a secondary energy source which means that we get it from the conversion of other sources of energy, like coal, natural gas, oil, nuclear power and other natural sources, which are called primary sources. The energy sources we use to make electricity can be renewable or non-renewable, but electricity itself is neither renewable or non-renewable.
(http://library.thinkquest.org/J001647F/)(http://42explore.com/electric.htm)
Electricity is a form of energy produced by the movement of electrons. Electricity is electrical power or an electric current. This form of energy can be sent through wires in a flow of tiny particles. It is used to produce light and heat and to run motors.
Electricity is a basic feature of all matter, of everything in the universe. Electrical force holds atoms and molecules together. Electricity determines the structure of every object that exists. Together with magnetism, it causes a force called electromagnetism, a fundamental force of the universe. Electricity or electrical signals are essential to many biological processes. In our bodies, electrical signals are carried through the nervous system, moving information to and from the brain. Electrical signals communicate to our brain what the eyes see, what the ears hear, and what the fingers feel.
Electrical signals from our brain causes our muscle movements. Electrical signals cause each heartbeat. One of the most important forms of electricity is in electrical current. During the industrial revolution of the 1800s, people began to find ways to use electricity to do work. Today electricity is used throughout our homes, at work, in communication, in transportation, and in medicine and science.
Electrically powered devices are prevalent. Relatively cheap electricity has made electrical appliances, machines, and other devices possible. A major reason electricity works is because of conductors. First metal, water, tall trees and tall items are good conductors because lightning is attracted to them. These materials have many mobile electrons.
Metal is an easy substance for lightning to travel through so metals are good conductors.However, rubber is a bad conductor because lightning bounces off of it. A bad conductor is called an insulator. An insulator has a few mobile electrons. It is important for us to know the difference between good conductors and insulators because if you're outside in an open field during a storm you will know where to go to be safe from the lightning. Truly, knowing the difference between conductors and insulators of electricity can save our lives.
It is a secondary energy source which means that we get it from the conversion of other sources of energy, like coal, natural gas, oil, nuclear power and other natural sources, which are called primary sources. The energy sources we use to make electricity can be renewable or non-renewable, but electricity itself is neither renewable or non-renewable.
(http://library.thinkquest.org/J001647F/)(http://42explore.com/electric.htm)
Sound by 2E1 Tan Hui Yu
What is sound?
Sound is a mechanical wave which results from the back and forth vibration of the particles of the medium through which the sound wave is moving. If a sound wave is moving from left to right through air, then particles of air will be displaced both rightward and leftward as the energy of the sound wave passes through it. The motions of the particles are parallel (and anti-parallel) to the direction of the energy transport. This is what characterizes sound waves in air as longitudinal waves.
How is sound being produced?
Sound are produced by the vibration of object . Sound is a physical entity, unlike noise which is the perception of sound. Sound is an high pressure wave front through a medium (such as air, or a liquid such as water, or a solid), wherein the wave front is followed by a reciprocal pressure differential behind it. Sound is produced when something disturbs the medium and sets in motion the molecules in the medium.
What affects sound?
One thing that can propagate sound is if you were to place something of which emits sound in a vacuum. The sound waves will propagate in the vacuum, because the matter which supports the sound called the medium no longer exists.
Source, http://en.wikipedia.org/wiki/Sound
Examples of stuff producing sound .
There are many things that can produce sound
Examples are radios , television , printers , fans .
What did I learn about the particular topic ?
I learn that sound is part of our life as it is everywhere . When we cough , a sound is made . When we talk or laugh with our friends , a sound is made . So it is very common to have sound everywhere .
Key points of the topic
Sound is a form of energy .
Are produced by the vibration of objects .
Sound travels through matter-solids, liquids and gases . Sound cannot travel through a vacuum .
Sources : Textbook resource , Source, http://en.wikipedia.org/wiki/Sound
Sound is a mechanical wave which results from the back and forth vibration of the particles of the medium through which the sound wave is moving. If a sound wave is moving from left to right through air, then particles of air will be displaced both rightward and leftward as the energy of the sound wave passes through it. The motions of the particles are parallel (and anti-parallel) to the direction of the energy transport. This is what characterizes sound waves in air as longitudinal waves.
How is sound being produced?
Sound are produced by the vibration of object . Sound is a physical entity, unlike noise which is the perception of sound. Sound is an high pressure wave front through a medium (such as air, or a liquid such as water, or a solid), wherein the wave front is followed by a reciprocal pressure differential behind it. Sound is produced when something disturbs the medium and sets in motion the molecules in the medium.
What affects sound?
One thing that can propagate sound is if you were to place something of which emits sound in a vacuum. The sound waves will propagate in the vacuum, because the matter which supports the sound called the medium no longer exists.
Source, http://en.wikipedia.org/wiki/Sound
Examples of stuff producing sound .
There are many things that can produce sound
Examples are radios , television , printers , fans .
What did I learn about the particular topic ?
I learn that sound is part of our life as it is everywhere . When we cough , a sound is made . When we talk or laugh with our friends , a sound is made . So it is very common to have sound everywhere .
Key points of the topic
Sound is a form of energy .
Are produced by the vibration of objects .
Sound travels through matter-solids, liquids and gases . Sound cannot travel through a vacuum .
Sources : Textbook resource , Source, http://en.wikipedia.org/wiki/Sound
Reflection of Light by 2E3 Ying jie
The bouncing of light off a mirror is called reflection.
Law of reflection
The ray of light approaching the mirror is known as the incident ray .The ray of light which leaves the mirror is known as the reflected ray .
At the point of incidence where the ray strikes the mirror, a line can be drawn perpendicular to the surface of the mirror, and this is called normal line.
The angle between the incident ray and the normal is known as the angle of incidence.
The angle between the reflected ray and the normal is known as the angle of reflection.
The law of reflection states that when a ray of light reflects off a surface THE ANGLE OF INCIDENCE = ANGLE OF REFLECTION .
Another law of reflection ,is Light travels in straight lines.
In a plane mirror ,
1. Image is Upright and of the same size of the object
2. Images lies as far behind the mirror as the object is in front of the mirror .
3. Image is laterally inverted .
4. image is always virtual image .
An image that cannot be formed on a screen is called VIRTUAL IMAGE.
Uses of the plane mirror,
Helps the driver to see the traffic behind , Makes room look bigger , Check their appearance .
Two types of reflection ,
Regular reflection – When a parallel beam of light hits a smooth surface , it is reflected as a parallel beam . An image is formed.
Diffuse reflection – When a beam of light hits the rough surface , individual rays are reflected in different directions. No image is formed .
Uses Of Curved mirrors ,
Convex Mirrors- Is a fish eye mirror or diverging mirror, is a curved mirror in which the reflective surface bulges toward the light source.
Upright images that are smaller than object. By the same time it allows many things to be seen.
Uses of Convex Mirrors :
1.Camera phones use convex mirrors to allow the user correctly aim the camera while taking a self-portrait.
2.The passenger-side mirror on a car is typically a convex mirror. It gives a safety warning "Objects in mirror are closer than they appear", to warn the driver of the convex mirror's distorting effects on distance perception.
Concave mirrors – Upright magnified images if the object is close to the mirror . If it is further away , the image is inverted .
Uses of Concave Mirrors :
Dentist mirror magnifies the image of our teeth .
Used to reflect light into microscope.
Law of reflection
The ray of light approaching the mirror is known as the incident ray .The ray of light which leaves the mirror is known as the reflected ray .
At the point of incidence where the ray strikes the mirror, a line can be drawn perpendicular to the surface of the mirror, and this is called normal line.
The angle between the incident ray and the normal is known as the angle of incidence.
The angle between the reflected ray and the normal is known as the angle of reflection.
The law of reflection states that when a ray of light reflects off a surface THE ANGLE OF INCIDENCE = ANGLE OF REFLECTION .
Another law of reflection ,is Light travels in straight lines.
In a plane mirror ,
1. Image is Upright and of the same size of the object
2. Images lies as far behind the mirror as the object is in front of the mirror .
3. Image is laterally inverted .
4. image is always virtual image .
An image that cannot be formed on a screen is called VIRTUAL IMAGE.
Uses of the plane mirror,
Helps the driver to see the traffic behind , Makes room look bigger , Check their appearance .
Two types of reflection ,
Regular reflection – When a parallel beam of light hits a smooth surface , it is reflected as a parallel beam . An image is formed.
Diffuse reflection – When a beam of light hits the rough surface , individual rays are reflected in different directions. No image is formed .
Uses Of Curved mirrors ,
Convex Mirrors- Is a fish eye mirror or diverging mirror, is a curved mirror in which the reflective surface bulges toward the light source.
Upright images that are smaller than object. By the same time it allows many things to be seen.
Uses of Convex Mirrors :
1.Camera phones use convex mirrors to allow the user correctly aim the camera while taking a self-portrait.
2.The passenger-side mirror on a car is typically a convex mirror. It gives a safety warning "Objects in mirror are closer than they appear", to warn the driver of the convex mirror's distorting effects on distance perception.
Concave mirrors – Upright magnified images if the object is close to the mirror . If it is further away , the image is inverted .
Uses of Concave Mirrors :
Dentist mirror magnifies the image of our teeth .
Used to reflect light into microscope.
Colours of Light by 2E2 Riesky
The colors are being produced when light passes through a prism and dispersion is the separation or splitting of white light into its separate colors.
The most famous example of dispersion is a rainbow, in which dispersion causes the spatial separation of a white light into components of different colors. However, dispersion is the most often explained for light waves, but it possibly occur for any kind of wave that interacts with a medium or passes through an inhomogeneous geometry. On the other hand dispersion also has an impact in my other circumstances.
Ordinary light (white light )is really a mixture of different colors. When a beam of white light passes through a glass prism, the light splits up into the colors you see is a rainbow. These colors are called the spectrum of white light.
The spectrum consists of seven colors: Red, Orange, Yellow, Green, Blue, Indigo and Violet or You can remember the order of the seven colors as a boy’s name: ROY G BIV. As these colors merge one into another gradually, it is difficult to say exactly where one colors ends and the next colors starts.
A rainbow is formed when sunlight (white light) passes through raindrops. These drops of water act as small prisms. The white light separates to form the colors of the spectrum.
Since white light consists of seven colors, we should be able to get white light again by combining the colors together. There are 2 ways:
By using a second prism
Spinning a color wheel
White light and light of other colors can be obtained by mixing just three colors – red, blue and green.
These colors are called the primary colors of light.
There are 2 basic ways colors can be mixed to make other colors. One is by combining color light. Mixing color light is called additive color mixing, because the combined colors are formed by the adding of light from 2 or more light sources together. Two or more lights added together will give more illumination than any of the lights by them selves.
If colored light is mixed together, the brightness of the colored lights are added together. This can be seen where the color illumination overlaps. The yellow mixed from red plus green will be brighter than either the red light or green light alone.
Likewise the color cyan is formed by adding green light and blue light. The cyan is also brighter than its two components.
green light + blue light = cyan
The same goes for the magenta and its mixture of red and blue.
red light + blue light = magenta
White light is formed where all three additive primary colors overlap. Since the white mixture results from the adding of all three color light sources, the white light mixture appears even brighter yet.
PRIMARY COLORS OF LIGHT
By varying the amount of the individual light sources, a full range of colors can be obtained. Television screens and PC monitors use the additive color process.
(http://en.wikipedia.org/wiki/Dispersion_(optics)
(http://home.att.net/~RTRUSCIO/COLORMX.htm)
Text book pg (128, 129 and 130)
The most famous example of dispersion is a rainbow, in which dispersion causes the spatial separation of a white light into components of different colors. However, dispersion is the most often explained for light waves, but it possibly occur for any kind of wave that interacts with a medium or passes through an inhomogeneous geometry. On the other hand dispersion also has an impact in my other circumstances.
Ordinary light (white light )is really a mixture of different colors. When a beam of white light passes through a glass prism, the light splits up into the colors you see is a rainbow. These colors are called the spectrum of white light.
The spectrum consists of seven colors: Red, Orange, Yellow, Green, Blue, Indigo and Violet or You can remember the order of the seven colors as a boy’s name: ROY G BIV. As these colors merge one into another gradually, it is difficult to say exactly where one colors ends and the next colors starts.
A rainbow is formed when sunlight (white light) passes through raindrops. These drops of water act as small prisms. The white light separates to form the colors of the spectrum.
Since white light consists of seven colors, we should be able to get white light again by combining the colors together. There are 2 ways:
By using a second prism
Spinning a color wheel
White light and light of other colors can be obtained by mixing just three colors – red, blue and green.
These colors are called the primary colors of light.
There are 2 basic ways colors can be mixed to make other colors. One is by combining color light. Mixing color light is called additive color mixing, because the combined colors are formed by the adding of light from 2 or more light sources together. Two or more lights added together will give more illumination than any of the lights by them selves.
If colored light is mixed together, the brightness of the colored lights are added together. This can be seen where the color illumination overlaps. The yellow mixed from red plus green will be brighter than either the red light or green light alone.
Likewise the color cyan is formed by adding green light and blue light. The cyan is also brighter than its two components.
green light + blue light = cyan
The same goes for the magenta and its mixture of red and blue.
red light + blue light = magenta
White light is formed where all three additive primary colors overlap. Since the white mixture results from the adding of all three color light sources, the white light mixture appears even brighter yet.
PRIMARY COLORS OF LIGHT
By varying the amount of the individual light sources, a full range of colors can be obtained. Television screens and PC monitors use the additive color process.
(http://en.wikipedia.org/wiki/Dispersion_(optics)
(http://home.att.net/~RTRUSCIO/COLORMX.htm)
Text book pg (128, 129 and 130)
Reflection of Light by 2E3 Li Yanbing
1) WHAT IS REFLECTION OF LIGHT?
The bouncing of light off a mirror is called reflection.
2) WHEN DOES IT HAPPEN?
Reflection happen when the image in a mirror is formed when light rays bounce off the mirror and travel to your eyes.
3) TYPES OF REFLECTION
There are basically two types of reflection:
Regular Reflection
When a parallel beam of light hits a smooth surface such as a plane mirror, it is reflected as a parallel beam. This is called a REGULAR reflection.That is when we look at a smooth surface,we see an image.
Diffuse Reflection
When a beam of light hits a rough surface, the individual rays are reflected in different direction. So no image is formed. This type of reflection is called DIFFUSE reflection.
4) USE OF REFLECTION OF LIGHT; EXAMPLES.
There are many examples of the use of reflection of light.
The rear view mirror of a car helps drivers to see traffic behind the car.
The use of plane mirrors to check one’s appearance.
Periscopes are made of two plane mirrors which see over obstacles such as walls.
Mirrors used in double-deck buses to help the driver to see the passengers on the upper deck.
Sources:
Heyworth, Rex M. Explore Your World with Science Discovery 2.
Diagram obtained from <http://www.rebeccapaton.net/rainbows/rflctn.gif>
The bouncing of light off a mirror is called reflection.
2) WHEN DOES IT HAPPEN?
Reflection happen when the image in a mirror is formed when light rays bounce off the mirror and travel to your eyes.
3) TYPES OF REFLECTION
There are basically two types of reflection:
Regular Reflection
When a parallel beam of light hits a smooth surface such as a plane mirror, it is reflected as a parallel beam. This is called a REGULAR reflection.That is when we look at a smooth surface,we see an image.
Diffuse Reflection
When a beam of light hits a rough surface, the individual rays are reflected in different direction. So no image is formed. This type of reflection is called DIFFUSE reflection.
4) USE OF REFLECTION OF LIGHT; EXAMPLES.
There are many examples of the use of reflection of light.
The rear view mirror of a car helps drivers to see traffic behind the car.
The use of plane mirrors to check one’s appearance.
Periscopes are made of two plane mirrors which see over obstacles such as walls.
Mirrors used in double-deck buses to help the driver to see the passengers on the upper deck.
Sources:
Heyworth, Rex M. Explore Your World with Science Discovery 2.
Diagram obtained from <http://www.rebeccapaton.net/rainbows/rflctn.gif>
Colours of light by 2E2 Liow Fang Yu
Colours of light
I learnt that sunlight may appear white, but it is actually made up of a mixture of seven colours. When the sunlight passes through the rain drop, the raindrop split the white sunlight into a range or spectrum of colours. The colours that makes the spectrum are red, orange, yellow, green, blue, indigo and violet.
We can see the colours of the spectrum, so it is called the visible spectrum . I learnt that I can also remember the order of the seven colours as a boy’s name: ROY G BIV
I learnt that when the splitting or separation of whit light into a spectrum of colours is called the dispersion of white light.
As the refracted colours of light leave the prism, they are bent again, but not in their original paths. This is because the face of the prism through which the light leaves is not parallel to the face through which it enters.
I learnt that to prove that white light is a mixture of different colours, another prism can be used to recombine the colours of its spectrum. Another way of combining the different colours of a spectrum is by spinning a rainbow-coloured disc called Newton’s disc.
I learnt that when a white light is a mixture of different colours, another prism can be used to recombine the colours of its spectrum. I learnt that white light and light of other colours can be obtained by lust mixing three colours. These three colours are red, blue and green. These three colours are called the primary colours of light.
Mixing the primary colours two at a time gives the following colours:
RED + BLUE = MAGENTA
RED + GREEN = YELLOW
BLUE + GREEN = CYAN
A colour television works in the same way. The picture on the television screen is made of dots of coloured light. A mixture of red, green and blue dots in different combinations and varying amounts of brightness produces the different colours in the picture.
These information can be found in : Interactive Science 2 (book) pg113 to119 and
Explore your world with science discovery 2 (book) pg128 to 130.
I learnt that sunlight may appear white, but it is actually made up of a mixture of seven colours. When the sunlight passes through the rain drop, the raindrop split the white sunlight into a range or spectrum of colours. The colours that makes the spectrum are red, orange, yellow, green, blue, indigo and violet.
We can see the colours of the spectrum, so it is called the visible spectrum . I learnt that I can also remember the order of the seven colours as a boy’s name: ROY G BIV
I learnt that when the splitting or separation of whit light into a spectrum of colours is called the dispersion of white light.
As the refracted colours of light leave the prism, they are bent again, but not in their original paths. This is because the face of the prism through which the light leaves is not parallel to the face through which it enters.
I learnt that to prove that white light is a mixture of different colours, another prism can be used to recombine the colours of its spectrum. Another way of combining the different colours of a spectrum is by spinning a rainbow-coloured disc called Newton’s disc.
I learnt that when a white light is a mixture of different colours, another prism can be used to recombine the colours of its spectrum. I learnt that white light and light of other colours can be obtained by lust mixing three colours. These three colours are red, blue and green. These three colours are called the primary colours of light.
Mixing the primary colours two at a time gives the following colours:
RED + BLUE = MAGENTA
RED + GREEN = YELLOW
BLUE + GREEN = CYAN
A colour television works in the same way. The picture on the television screen is made of dots of coloured light. A mixture of red, green and blue dots in different combinations and varying amounts of brightness produces the different colours in the picture.
These information can be found in : Interactive Science 2 (book) pg113 to119 and
Explore your world with science discovery 2 (book) pg128 to 130.
Electricity by 2E2 Siti Azwani
Electricity
i) I have learnt that electricity is a controllable and convenient form of energy used in everyday life. Electricity is the flow of electrons. Without it, we may not be able to perform our everyday routine. Mainly, we used electricity for work, play, in the house and at work, (and at school).
ii) Electricity is a basic part of nature and it is one of our most widely used forms of energy. We get electricity, which is a secondary energy source, from the conversion of other sources of energy, like coal, natural gas, oil, nuclear power and other natural sources, which are called primary sources.
In every electricity, there will always be an electric current. An electric current is a flow of electric charge around a circuit. The charge is already in the wires. This charge is evenly spread out through the wires. As soon as you close the switch, the cell starts to push on the charge. So all the charge starts moving at once. An electric cell gives energy to the electrons and pushes them around a circuit.
Voltage is a measure of how much energy the electrons receive.
iv) acknowledge from: sec 2 Science textbook and wikipedia.com
i) I have learnt that electricity is a controllable and convenient form of energy used in everyday life. Electricity is the flow of electrons. Without it, we may not be able to perform our everyday routine. Mainly, we used electricity for work, play, in the house and at work, (and at school).
ii) Electricity is a basic part of nature and it is one of our most widely used forms of energy. We get electricity, which is a secondary energy source, from the conversion of other sources of energy, like coal, natural gas, oil, nuclear power and other natural sources, which are called primary sources.
In every electricity, there will always be an electric current. An electric current is a flow of electric charge around a circuit. The charge is already in the wires. This charge is evenly spread out through the wires. As soon as you close the switch, the cell starts to push on the charge. So all the charge starts moving at once. An electric cell gives energy to the electrons and pushes them around a circuit.
Voltage is a measure of how much energy the electrons receive.
iv) acknowledge from: sec 2 Science textbook and wikipedia.com
Reflection of Light by 2E4 Gao YanTing
Reflection is the bouncing of light off an object,when light falls on the object.
The laws of reflection :
The angle of incidence is equal to the angle of reflection.
The incident ray , the reflected ray and the normal at the point of incidence all lie on the same plane.
There are two types of reflection :
Regular reflection ---- a parallel beam of light is reflected as a parallel beam in the same direction to form clear images,occurs on smooth surfaces.
Diffused reflection ----- a parallel beam of light is reflected in different directions without forming any image,occurs on rough surfaces.
Uses of Plane Mirror
Help the driver to see traffic behind
Make a room look bigger
Check their appearance
Uses of Curved Mirrors
Convex --- Security mirrors are used in shops
Blind corner mirrors help drivers to see objects around the corner
Concave ---- Aconcave mirror is used to reflect light into the microscope
A dentist's mirror magnifies the image of your teeth.
From:Git it right
and Text book
The laws of reflection :
The angle of incidence is equal to the angle of reflection.
The incident ray , the reflected ray and the normal at the point of incidence all lie on the same plane.
There are two types of reflection :
Regular reflection ---- a parallel beam of light is reflected as a parallel beam in the same direction to form clear images,occurs on smooth surfaces.
Diffused reflection ----- a parallel beam of light is reflected in different directions without forming any image,occurs on rough surfaces.
Uses of Plane Mirror
Help the driver to see traffic behind
Make a room look bigger
Check their appearance
Uses of Curved Mirrors
Convex --- Security mirrors are used in shops
Blind corner mirrors help drivers to see objects around the corner
Concave ---- Aconcave mirror is used to reflect light into the microscope
A dentist's mirror magnifies the image of your teeth.
From:Git it right
and Text book
Reflection of Light by 2E4 Ding Ruxin
1.Reflection of light is very predictable. The Law of Reflection describes it simply as "The angle of incidence is equal to the angle of reflection."
2.Law of reflection: ' = where is the angle of incidence and ' is the reflected angle from the normal.
Yeah, that is great for flat surfaces but what about curved surfaces? It works the same way. Simply draw the tangent line to the point of the curve and reflect the light according to the tangent line.
There are actually two types of reflections: specular and diffused.
Specular reflection is reflection from a smooth surface. When light strikes this smooth surface, all the reflected rays are in line with each other.
Diffused reflection is reflection from a rough surface. The small bumps and irregularities on a rough surface will cause each of the light rays to reflect in different directions, all following the law of reflection of course.
Any incident ray traveling parallel to the principal axis on the way to a concave mirror will pass through the focal point upon reflection.
Any incident ray passing through the focal point on the way to a concave mirror will travel parallel to the principal axis upon reflection.
3 .Materials that reflect neutrons, for example beryllium, are used in nuclear reactors and nuclear weapons. In the physical and biological sciences, the reflection of neutrons off atoms within a material is commonly used to determine its internal structures.
4. http://library.thinkquest.org/27356/p_reflection.htm
2.Law of reflection: ' = where is the angle of incidence and ' is the reflected angle from the normal.
Yeah, that is great for flat surfaces but what about curved surfaces? It works the same way. Simply draw the tangent line to the point of the curve and reflect the light according to the tangent line.
There are actually two types of reflections: specular and diffused.
Specular reflection is reflection from a smooth surface. When light strikes this smooth surface, all the reflected rays are in line with each other.
Diffused reflection is reflection from a rough surface. The small bumps and irregularities on a rough surface will cause each of the light rays to reflect in different directions, all following the law of reflection of course.
Any incident ray traveling parallel to the principal axis on the way to a concave mirror will pass through the focal point upon reflection.
Any incident ray passing through the focal point on the way to a concave mirror will travel parallel to the principal axis upon reflection.
3 .Materials that reflect neutrons, for example beryllium, are used in nuclear reactors and nuclear weapons. In the physical and biological sciences, the reflection of neutrons off atoms within a material is commonly used to determine its internal structures.
4. http://library.thinkquest.org/27356/p_reflection.htm
Reflection of Light by 2E4 Zhang Ling
What is reflection?
1．Reflection is the change in direction of a wave front at an interface between two different media so that the wave front returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves.
Reflection of light may be specular (that is, mirror-like) or diffuse (that is, not retaining the image, only the energy) depending on the nature of the interface. Furthermore, if the interface is between dielectric-conductor or dielectric-dielectric media, the phase of the reflected wave may or may not be inverted, respectively.
2．（1）Reflection of light
In the diagram, a light ray PO strikes a vertical mirror at point O, and the reflected ray is OQ. By projecting an imaginary line through point O perpendicular to the mirror, known as the normal, we can measure the angle of incidence, θi and the angle of reflection, θr. The law of reflection states that θi = θr, or in other words, the angle of incidence equals the angle of reflection.
In fact, reflection of light may occur whenever light travels from a medium of a given refractive index into a medium with a different refractive index.
（2）Laws of regular reflection
If the reflecting surface is very smooth, the reflection of light that occurs is called specular or regular reflection. The laws of reflection are as follows:
The incident ray, the reflected ray and the normal to the reflection surface at the point of the incidence lie in the same plane.
The angle which the incident ray makes with the normal is equal to the angle which the reflected ray makes to the same normal.
（3）Diffuse reflection
When light strikes a rough or granular surface, it bounces off in all directions due to the microscopic irregularities of the interface. Thus, an 'image' is not formed. This is called diffuse reflection.
3．Light bounces exactly back in the direction from which it came due to a nonlinear optical process. In this type of reflection, not only the direction of the light is reversed, but the actual wavefronts are reversed as well. A conjugate reflector can be used to remove aberrations from a beam by reflecting it and then passing the reflection through the aberrating optics a second time.
4．http://en.wikipedia.org/wiki/Reflection_%28physics%29#Reflections
1．Reflection is the change in direction of a wave front at an interface between two different media so that the wave front returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves.
Reflection of light may be specular (that is, mirror-like) or diffuse (that is, not retaining the image, only the energy) depending on the nature of the interface. Furthermore, if the interface is between dielectric-conductor or dielectric-dielectric media, the phase of the reflected wave may or may not be inverted, respectively.
2．（1）Reflection of light
In the diagram, a light ray PO strikes a vertical mirror at point O, and the reflected ray is OQ. By projecting an imaginary line through point O perpendicular to the mirror, known as the normal, we can measure the angle of incidence, θi and the angle of reflection, θr. The law of reflection states that θi = θr, or in other words, the angle of incidence equals the angle of reflection.
In fact, reflection of light may occur whenever light travels from a medium of a given refractive index into a medium with a different refractive index.
（2）Laws of regular reflection
If the reflecting surface is very smooth, the reflection of light that occurs is called specular or regular reflection. The laws of reflection are as follows:
The incident ray, the reflected ray and the normal to the reflection surface at the point of the incidence lie in the same plane.
The angle which the incident ray makes with the normal is equal to the angle which the reflected ray makes to the same normal.
（3）Diffuse reflection
When light strikes a rough or granular surface, it bounces off in all directions due to the microscopic irregularities of the interface. Thus, an 'image' is not formed. This is called diffuse reflection.
3．Light bounces exactly back in the direction from which it came due to a nonlinear optical process. In this type of reflection, not only the direction of the light is reversed, but the actual wavefronts are reversed as well. A conjugate reflector can be used to remove aberrations from a beam by reflecting it and then passing the reflection through the aberrating optics a second time.
4．http://en.wikipedia.org/wiki/Reflection_%28physics%29#Reflections
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