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Matthew Hasjim

on 6 March 2012

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Transcript of Light

Light by Matthew Hasjim, Louis Takchi,
Leonard Kowik and Luca Moretti What is Light? Hope you had an entertaining time! Light is simply a range of electromagnetic radiation (emitted energy from an electric and magnetic source) that can be detected by the human eye. Light is created in the Sun when hydrogen nuclei
are fused together to form helium, releasing a lot of energy, light and heat. This process is called nuclear fusion. The visible light we see is produced when electromagnetic electrons emit energy waves, due to the fluctuation of the energy levels of the electrons. During this fluctuation, a photon is produced, which is glowing in light and emitting energy. The brighter the light, the more photons there are. So...
How has the understanding of the properties of light affected society? In order to answer this, we need to further look at the properties of light. Properties of Light Reflection Absorption Dispersion Refraction is a process in which light bends through an object. Light travels in a straight line when that straight line goes in an object such as glass or water it bends. Therefore when we are swimming in a pool, we can’t see our body directly because it can’t reflect as good as a mirror because the light that goes through the water in the pool, bends, creating a blurry image of your body when you’re in the pool. When we see glass it’s either a convex or a concave glass. A convex glass makes the image your looking bigger and a concave does the opposite it makes the image smaller that’s because the light that goes in the glass makes it either smaller or a bigger image depends how the light bends Refraction The picture above displays a pencil in a cup. When the light goes through the water it bends thus creating the pencil looks like it’s bent. This picture above displays a man fishing in a pool or river. Since light bends through water it makes the image bent therefore creating the image that the fish is close but it’s actually farther. This diagram shows white light being separated
into the colour spectrum (all the colours of the rainbow) The Dispersion of light is the separation of light into
colours by refraction (bending light outward) or
diffraction (when light hits an obstacle, such as sharp
edges or narrow slits), with the formation of the colour spectrum There is another type of reflection, apart from the usual. The phenomenon is called total internal reflection, when the light incidence ray surpasses a certain angle (called 'critical angle') that the ray cannot be effectively refracted through the other side anymore, instead it is reflected and bounced back. For example, when a rainbow forms in the sky after rain. The white light is being bent first and then internally reflected inside the raindrop. The law of reflection applies. Another example would be when white light is directed into a glass prism; the prism breaks and splits the light (dispersion) into all 7 colours of the rainbow, which are in the visible spectrum speed of electromagnetic waves. These 7 colours are violet, indigo, blue, green, yellow, orange and red, from stronger wavelength to weaker wavelength. For example, when a rainbow is formed, white light from the Sun splits up inside the raindrops and disperses into the colour spectrum. The electromagnetic spectrum, from strongest
rays to weakest rays, with visible light in the centre Light is absorbed into particular colours or objects. The reason we see different colours is that different objects reflect and absorb different colours.This shows that black colours absorb all light, white reflects all light and the other colours absorb all light except for some of the light. Absorption is when light energy is taken in
by a substance. Examples include wearing a
black shirt on a hot day and the
shirt becoming hot In absorption, the strength of the incoming light wave is at or near the energy levels of the electrons that are being absorbed into the object. Reflection is the bouncing back of light from a surface. The
law of reflection states that the angle of incidence (the angle
of which the light approaches the surface compared to a
perpendicular line) and the angle of reflection (the angle
of which the light bounces off the surface compared to a
perpendicular line) has to be equal. Light behaves differently when reflected off certain objects. When light is reflected off smooth surfaces, the reflection is mostly normal and regular. But when light reflects of rough objects, light diffuses and reflects towards different areas. This is due to the many sides of the rough objects. Light reflects off these sides (which are placed at different angles) and therefore still follow the law of reflection. Equal Angles Example of reflection would be when we see colours. For example, if I see a yellow shirt, it means that the material that is used in the shirt absorbs all light, but reflects yellow light only. Another example would be turning on the light bulb and then looking into a mirror. Light from the light bulb reaches the mirror and bounces off at the same angles (law of reflection) This is a fully labelled ray diagram on the reflection of light. It also indicates that the angle of which light comes in and hits the surface (angle of incidence) is equal to the angle of which the light bends afterwards (reflection angle) This diagram shows total internal reflection and the
process. The drawing on the right shows the critical angle
(dependant on the medium that the light goes through). The critical angle is measured when the refracten ray is perpendicular (90 degrees) to the normal, stralight ray.The middle drawing shows the normal refraction (in green). If the angle of incidence (shown in blue) is more than the critical angle (in red), the light will internally reflect (as shown in left diagram. How does light travel? Light moves in waves. It transports energy from its source to its surroundings. Light travelling from the Sun takes about 8.5 minutes to reach the earth. Scientists have correctly measured the speed of light to be 299,792,458 m/s The wavelength is the distance from the peak of the wave to the peak next to it. Amplitude is the height from
the peak (or crest) of the wave from
the normal straight line. We can’t see through water clearly because the light is bent so we can only see water itself and a blurry image on the background. How does light give us life! Light gives us plants, trees, animals and oxygen Light gives us energy Light gives us sight Light gives us heat and warmth Law of Conservation of Energy For example, when light is absorbed into an object, the energy levels still stay the same (no energy lost) When light 'fades away', this is due to the electromagnetic wavelength becoming more longer, stretched and therefore more weaker. These light rays are then absorbed into materials or converted into heat energy. Light is a form of energy, and therefore, the Law of Conservation of energy applies. "Energy cannot be created nor destroyed, it can only be converted from one form into another." Refraction Without the understanding of refraction, we would’ve never invented the telescope to see stars and planets and the microscope to see small particles that you can’t see with the naked eye. Today we understand that refraction is caused by light slowing down through an object. The understanding of the refraction of light has allowed humans to accurately bend light for use in glasses, microscopes and telescopes. Reflection Without the understanding of reflection, we never would’ve seen ourselves in the mirror, nor could we have known why we see certain colours on certain objects.

Understanding the laws of reflection impacts on the society because without knowledge of them, we wouldn’t have invented mirrors, telescopes, microscopes and more. Absorption For example we know that darker colours such as black absorbs more light which creates heat that’s why on hot days people rarely wear black. Also, in building and construction, some materials have to absorb heat, like how insulators absorb heat and keep it inside the house. Understanding the laws of absorption affects society by explaining to us which colours/objects would not only absorb light, but to also absorb heat. Dispersion For example, without understanding dispersion, we could not have known how rainbows are formed, the colours of the spectrum, or what white light is made up of. Understanding the laws of dispersion affects society by letting us see and identify the colours of the colour spectrum, and by controlling these dispersions, we can accurately calculate the speed of each light colour, which could be used to create artificial coloured light.
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