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
Friday, June 20, 2008
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
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