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*
Showing posts with label 2e4. Show all posts
Showing posts with label 2e4. Show all posts
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
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
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
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
Thursday, June 19, 2008
Electricity by 2E4 Nurhakim
What is the importance of using Electricity?
Electricity is a form of energy. Around us, we are almost surrounded by Electricity.
Examples, Computer & Hand phone. Without Electricity, modern life would be impossible. Imagine there is a Blackout; the life of an electric still goes on as it works on a battery.
Sources of Electricity
There are 2 main sources, main electricity and electric cells.
Main Electricity
Main Electricity is generated by in power plants or power station. There are another 2 types of main electricity.
Re-useable energy
Non-renewable Energy
Electric Cells
Electric Cells gives out very little energy. These are used in many portable electrical devices and are safe to use.
Most of the Electric uses are mainly for…
Communication [To make communication in Space and the Earth]
Electronics [Electronic gadgets]
Telephones [Another type of communication]
Faxes & Modem [Another type of communication]
Radio [Another type of communication]
Television [Another type of communication]
Computers [Another type of communication]
& many more
Electricity is a form of energy. Around us, we are almost surrounded by Electricity.
Examples, Computer & Hand phone. Without Electricity, modern life would be impossible. Imagine there is a Blackout; the life of an electric still goes on as it works on a battery.
Sources of Electricity
There are 2 main sources, main electricity and electric cells.
Main Electricity
Main Electricity is generated by in power plants or power station. There are another 2 types of main electricity.
Re-useable energy
Non-renewable Energy
Electric Cells
Electric Cells gives out very little energy. These are used in many portable electrical devices and are safe to use.
Most of the Electric uses are mainly for…
Communication [To make communication in Space and the Earth]
Electronics [Electronic gadgets]
Telephones [Another type of communication]
Faxes & Modem [Another type of communication]
Radio [Another type of communication]
Television [Another type of communication]
Computers [Another type of communication]
& many more
Reflection of Light by 2E4 Wang Si Qian
flat mirror called a pane 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 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(the angle of reflection) .These two angles always are always equal no matter how light rays strikes the mirror. This generalization is called the law of reflection .
In a plane mirror, - the image is upright and of the same size as the object
-the image lies as far behind the mirror as the object is in front of the mirror.
-an image is laterally inverted.
-the image formed is always a virtual image.
Type of reflection -regular reflection and diffuse 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.
-an image is formed.
Diffuse reflection:
-when a beam of light hits a rough surface, the individual rays are reflected in different directions.
-no image is formed.
The use of plane mirror: -people use plane mirrors to check their appearance.
-plane mirrors on walls make the room bigger.
-the rear view mirror of a car helps the diver to see traffic behind the car.
-two plane mirrors are used in a periscope to reflect and change the direction of light.
-a telescope uses mirrors to produce very clear image.
Laws in this topic
–light travels in straight lines.
-for reflection in a plane mirror, the angle of incidence is equal to the angle of reflection.
-the angle of incidence=the angle of reflection.
Resources are from: textbook and www.treemo.com/users/somniumfate/channel/item/62506
In a plane mirror, - the image is upright and of the same size as the object
-the image lies as far behind the mirror as the object is in front of the mirror.
-an image is laterally inverted.
-the image formed is always a virtual image.
Type of reflection -regular reflection and diffuse 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.
-an image is formed.
Diffuse reflection:
-when a beam of light hits a rough surface, the individual rays are reflected in different directions.
-no image is formed.
The use of plane mirror: -people use plane mirrors to check their appearance.
-plane mirrors on walls make the room bigger.
-the rear view mirror of a car helps the diver to see traffic behind the car.
-two plane mirrors are used in a periscope to reflect and change the direction of light.
-a telescope uses mirrors to produce very clear image.
Laws in this topic
–light travels in straight lines.
-for reflection in a plane mirror, the angle of incidence is equal to the angle of reflection.
-the angle of incidence=the angle of reflection.
Resources are from: textbook and www.treemo.com/users/somniumfate/channel/item/62506
Reflection of Light by 2E4 Fang Shu Yang
When reflection of light photoemission to two kind of different natures, then has part of light, from the interface shoots in the original nature the phenomenon, is called the reflection of light. law of reflection:
(1) incident ray, reflect rays and normal on identical plane mirror, and incident ray, reflect rays in normal both sides.
(2) the incidence angle is equal to the reflection angle. the surface smooth object, easy to form the light the regular reflection, forms the dazzling glare, instead looks at not the clear object. in the usual situation may distinguish shape and the existence the object, therefore is as a result of the light diffusion. after sunset, can see the object temporarily, is therefore because in the air the dust causes the light diffusion. Regardless of being the regular reflection or the diffuse reflection, must observe the law of reflection。
When the light shines after the object on, some part of light have been absorbed (with light frequency related), other cannot the light which absorbs be the reflected light. The reflection divides into the regular reflection and the diffuse reflection.
(1) incident ray, reflect rays and normal on identical plane mirror, and incident ray, reflect rays in normal both sides.
(2) the incidence angle is equal to the reflection angle. the surface smooth object, easy to form the light the regular reflection, forms the dazzling glare, instead looks at not the clear object. in the usual situation may distinguish shape and the existence the object, therefore is as a result of the light diffusion. after sunset, can see the object temporarily, is therefore because in the air the dust causes the light diffusion. Regardless of being the regular reflection or the diffuse reflection, must observe the law of reflection。
When the light shines after the object on, some part of light have been absorbed (with light frequency related), other cannot the light which absorbs be the reflected light. The reflection divides into the regular reflection and the diffuse reflection.
Refraction of Light by 2E4 Zhang Meiting
Download the original attachment
Refraction Of Light
In this blog reflection, I have chosen refraction of light as my topic. In this topic, I have learnt that refraction of light is when the light goes in or out of the glass, it changes direction because the rays bend. One example I have learn is when I put a cup of water on the table with a straw inside, I realise that the straw has cut into half but as when I take the straw out of the cup, again I realise that the straw is still in it original shape and length. And this experiment had showed me that light changes direction when it passes from one transparent material into another.
And in this particular topic, I know that light bends because its speed changes as it moves from 1 transparent material to another. Also, light travels slower in more dense materials than in less dense materials that why light travels slower in glass than in air. So, when a beam of light passes from air into a glass block, it slows down and bends towards the normal but when the beam of light comes out of glass into air, it will bend away from the normal.
From this particular topic, I learn that when the boundary of 2 optical media, there will be a sudden change in the speed of light to bend, resulting in refraction. Since I know that refraction is caused by a change in speed of light, the relationship between the angle of incidence and the angle of reflection has to be related to this change in speed of light in a medium.
For the effects of refraction I learn so far, a swimming pool appears shallower than it really is. This is because light from an object bends as it comes out of water. But human brain thinks that 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 of this topic are, light is bend or refracted when it passes from one transparent material into another, such as from air to glass and vice versa. For the refraction I have learn, there are two effects, which are, an object in water appears nearer to the surface than it really is and an object such as a stick placed in water appears to be bent.
All these are found in:
sec2 textbook
sec2 theory workbook
handout
sec4 physics textbook
http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/refr.html
Reflection of Light by 2E4 Chanita
Light of "Reflection": is "a ray of light bounces off of a mirror.
Types of reflection
Regular Reflection
- with surfaces so smooth are smaller than the wavelength of light, the law of reflection applies on a large scale. All the light traveling in one direction and reflecting from the mirror is reflected in one direction.
Diffuse reflection
– with light being reflected in all directions. If the irregularities on the surface of an object are larger than the wavelength of light, which is usually the case, the light reflects off in all directions.
Uses of reflection of light
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. 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).
Facts:
1. The woman's image is as far behind the flat mirror as she is in front of it. >>>
2.The "woman" in the mirror is combing her hair with her left hand.>>>
When the water is still, reflection is specular. The image blurs when the water is rough
Images in convex mirrors are always smaller
Images in concave mirrors are always bigger
Do You Know that:?
*Light slows down, bends toward the normal and has a shorter wavelength when it enters a higher (n) value medium.
*The Rainbow is a reflection of perfect balance of the physical world
Thinking Time:
All you brainiacs out there, if light reflect off an object... then what colour is the object itself? If white light contains all the colours of the visible spectrum, and say, it reflects off of an object that is red, the object itself absorbs all the colours of the spectrum except red. So then is that object in fact red? Or is it every other colour except red? What about a 'black’ light. If the color black lacks all colours, why then when you shine a black light on an object, it appears as its 'negative' color, such as reds or yellows appear green. Not all colors but many colors exhibit this phenomenon. An object that is "white' in color glows almost fluorescent in black light... What is it exactly are we seeing when we see the 'colour' of an object?
Answer: The colour we are seeing is in fact the light being reflected off the object as well as the reception of our rod and cone cells in the retina of the eye. The cone cells are the ones that respond to different colors. There are groups of cone cells that respond to red, or blue or yellow so basically what we 'perceive' as color depends on both these factors. And really, perception is on an individual basis. Theoretically, what you perceive as red, I may perceive as blue. It is very much possible. Colours, I think are an illusion that we create with our brains. They are just that. They themselves have no 'color'. Its like our brain receives this upside down weird black and white photo, and puts it upright, colours it up to make it attractive. And that is what we see as 'beautiful' and colourful. As for reality...that, we may never know.
Game: http://www.phy.ntnu.edu.tw/oldjava/optics/mirrorgame_e.html
Resources:
www.yahoo.com/question/index?qid=20070819060134AAanM50 - 47k –
http://www.google.co.th/
Types of reflection
Regular Reflection
- with surfaces so smooth are smaller than the wavelength of light, the law of reflection applies on a large scale. All the light traveling in one direction and reflecting from the mirror is reflected in one direction.
Diffuse reflection
– with light being reflected in all directions. If the irregularities on the surface of an object are larger than the wavelength of light, which is usually the case, the light reflects off in all directions.
Uses of reflection of light
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. 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).
Facts:
1. The woman's image is as far behind the flat mirror as she is in front of it. >>>
2.The "woman" in the mirror is combing her hair with her left hand.>>>
When the water is still, reflection is specular. The image blurs when the water is rough
Images in convex mirrors are always smaller
Images in concave mirrors are always bigger
Do You Know that:?
*Light slows down, bends toward the normal and has a shorter wavelength when it enters a higher (n) value medium.
*The Rainbow is a reflection of perfect balance of the physical world
Thinking Time:
All you brainiacs out there, if light reflect off an object... then what colour is the object itself? If white light contains all the colours of the visible spectrum, and say, it reflects off of an object that is red, the object itself absorbs all the colours of the spectrum except red. So then is that object in fact red? Or is it every other colour except red? What about a 'black’ light. If the color black lacks all colours, why then when you shine a black light on an object, it appears as its 'negative' color, such as reds or yellows appear green. Not all colors but many colors exhibit this phenomenon. An object that is "white' in color glows almost fluorescent in black light... What is it exactly are we seeing when we see the 'colour' of an object?
Answer: The colour we are seeing is in fact the light being reflected off the object as well as the reception of our rod and cone cells in the retina of the eye. The cone cells are the ones that respond to different colors. There are groups of cone cells that respond to red, or blue or yellow so basically what we 'perceive' as color depends on both these factors. And really, perception is on an individual basis. Theoretically, what you perceive as red, I may perceive as blue. It is very much possible. Colours, I think are an illusion that we create with our brains. They are just that. They themselves have no 'color'. Its like our brain receives this upside down weird black and white photo, and puts it upright, colours it up to make it attractive. And that is what we see as 'beautiful' and colourful. As for reality...that, we may never know.
Game: http://www.phy.ntnu.edu.tw/oldjava/optics/mirrorgame_e.html
Resources:
www.yahoo.com/question/index?qid=20070819060134AAanM50 - 47k –
http://www.google.co.th/
Reflection of Light by 2E4 HA SEONG EUN
Reflection of light occurs when the waves encounter a surface or other boundary that does not absorb the energy of the radiation and bounces the waves away from the surface. The simplest example of visible light reflection is the surface of a smooth pool of water, where the light is reflected in an orderly manner to produce a clear image of the scenery surrounding the pool.
When does it happen
Reflection of light occurs when the waves encounter a surface or other boundary that does not absorb the energy of the radiation and bounces the waves away from the surface. This tutorial explores the incident and reflected angles of a single light wave impacting on a smooth surface.
Types of reflection
Regular reflection occurs when incident parallel rays are also reflected parallel from a smooth surface. If the surface is smooth, parallel incident rays are no longer parallel when reflected. This results in diffuse.
The laws of reflection apply to diffuse reflection. The irregular surface can be considered to be made up of a large number of small planar reflecting surfaces positioned at slightly different angles. Indirect (or diffuse) lighting produces soft shadows. It produces less eye strain than harsher, direct lighting.
Uses of reflection
A refracting telescope uses convex lenses to gather a large amount of light and focus it onto a smaller area. Refracting telescopes use two lenses—an eyepiece lens and an objective lens. When light passes through the objective lens, the lens focuses the light at a certain distance away from the lens. This distance is called the focal length of the lens.
Plane mirror
The rear view mirror of a car helps the drivers to see traffic behind the car.
Plane mirrors on walls make a room look bigger.
Convex mirror
Security mirrors are used in shops.
Concave mirror
A concave mirror is used to reflect light into the microscope.
When does it happen
Reflection of light occurs when the waves encounter a surface or other boundary that does not absorb the energy of the radiation and bounces the waves away from the surface. This tutorial explores the incident and reflected angles of a single light wave impacting on a smooth surface.
Types of reflection
Regular reflection occurs when incident parallel rays are also reflected parallel from a smooth surface. If the surface is smooth, parallel incident rays are no longer parallel when reflected. This results in diffuse.
The laws of reflection apply to diffuse reflection. The irregular surface can be considered to be made up of a large number of small planar reflecting surfaces positioned at slightly different angles. Indirect (or diffuse) lighting produces soft shadows. It produces less eye strain than harsher, direct lighting.
Uses of reflection
A refracting telescope uses convex lenses to gather a large amount of light and focus it onto a smaller area. Refracting telescopes use two lenses—an eyepiece lens and an objective lens. When light passes through the objective lens, the lens focuses the light at a certain distance away from the lens. This distance is called the focal length of the lens.
Plane mirror
The rear view mirror of a car helps the drivers to see traffic behind the car.
Plane mirrors on walls make a room look bigger.
Convex mirror
Security mirrors are used in shops.
Concave mirror
A concave mirror is used to reflect light into the microscope.
Refraction of Light by 2E4 Lavanya
REFRACTION
WHAT IS REFRACTION OF LIGHT?
WHEN DOES IT HAPPEN?
HOW AND WHEN WILL LIGHT BEND?
WHAT IS REFRACTIVE INDEX?
EFFECTS OF REFRACTION
Refraction of light refers to the change in the
direction of light.
Refraction of light occurs when it passes from
one transparent material into another.
3a.When light moves from glass to air (a less dense
material), it speeds up and is refracted away from
the normal.
Light twists outward when entering
Medium of lower index of refraction
3b. When light moves from air to glass (a denser material),
it slows down and is refracted towards the normal.
Light twists inward when entering
medium of higher index of refraction
4. The effects of refraction are causing an object to appear nearer than it actually is when a transparent material is on top.
WHAT IS REFRACTION OF LIGHT?
WHEN DOES IT HAPPEN?
HOW AND WHEN WILL LIGHT BEND?
WHAT IS REFRACTIVE INDEX?
EFFECTS OF REFRACTION
Refraction of light refers to the change in the
direction of light.
Refraction of light occurs when it passes from
one transparent material into another.
3a.When light moves from glass to air (a less dense
material), it speeds up and is refracted away from
the normal.
Light twists outward when entering
Medium of lower index of refraction
3b. When light moves from air to glass (a denser material),
it slows down and is refracted towards the normal.
Light twists inward when entering
medium of higher index of refraction
4. The effects of refraction are causing an object to appear nearer than it actually is when a transparent material is on top.
Refraction of light by 2E4 Chua Xue Ting
Refraction of light is not difficult to learn. Refraction happen everywhere, and anytime it can happen when a person uses a mirror to see their look, and can happen when a light shine on a metal object. Refraction is a bouncing off light through refraction mirror. There are two type of refraction mirror, concave and convex mirror. Concave mirror is use as Security
Mirror and use at blind corner. Convex mirror is use as face mirror. Refraction of light cannot occur when there is no refracted object.
There is a lot of refraction object- example metal spoon, shiny watch and keychain. These object is a good refraction object. Normally, a good refraction object is easier to catch fire than non refraction. This is because refraction object get more light to heat up.
Light rare cause the light to bend when pass through the glass. This is because the air is denser than the glass, so when light rare passes through the glass.
Mirror and use at blind corner. Convex mirror is use as face mirror. Refraction of light cannot occur when there is no refracted object.
There is a lot of refraction object- example metal spoon, shiny watch and keychain. These object is a good refraction object. Normally, a good refraction object is easier to catch fire than non refraction. This is because refraction object get more light to heat up.
Light rare cause the light to bend when pass through the glass. This is because the air is denser than the glass, so when light rare passes through the glass.
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