Overview
1. Lightwaves and Frequency
2. The Visible Light Spectrum
3. Effecting Factors on Light
Light Waves
Light is detected by the human eye however unlike sound light does not need to a medium to travel through so this means that once emitted from the sun it can travel through the cold dark vacuum of space to, after 8 minutes and 20 seconds, reach Earth.
Light is a transverse wave, similar to a ripple on the surface of a liquid.
Light is transmitted in electromagnetic waves in a certain form of radio wave and this basically means that our eyes are a sort of receiver. Humans can only see about 400 THz to 750 THz (Tera-Hertz). This range tends to be portrayed using colours starting at red for lower frequencies and then moving to violet for the higher frequencies.
source - the lecture slides
source - the lecture slides
The frequency of a light wave is related to the medium at which the wave is travelling through. The speed the wave can reach and travel at is equal to the wave length x the frequency. This can be shown mathematically through a simple equation.
The Visible Light Spectrum
A prism with a white light shone through it can be used to show the colours of the rainbow. These colours also show the light spectrum. The cover of Pink Floyd's album can be used to show this perfectly.
source - http://fc07.deviantart.net/fs71/i/2012/067/6/8/dark_side_of_the_moon_wallpaper_pack_by_alphasnail-d4s4nhs.png
As we can see the top of the rainbow starts at red and the bottom is violet. This is the visible light spectrum that is shown with high frequencies and low frequencies.
Waves with a frequency just under the range of the human eye is known as infrared light. This wavelength is usually longer than 700nm. A laser that is used to operate on CD's works at 780nm. Waves with a frequency just over the range of the human eye is known as ultraviolet light and these have a shorter wavelength of 400nm. Some animals can hear sounds that are outwith the human range and the same goes for their visual capacity. Some animals have the ability to see ranges that humans cannot such as bees can see in ultraviolet.
source - http://www.wildlifeonline.me.uk/images/graphics/visible_light.png
Affecting Factors on Light
Light can be affected and changed by the environment around it. It can be absorbed, scattered, refracted, transmitted and reflected. Depending on the what the object is made from means that the light can be transmitted differently. A pane of glass that is clean and does not distort light is only visible because of the reflection of its surroundings otherwise it'd be invisible to the human eye.
The intensity of a light source can be mathematically calculated by using the inverse-square law. This is when we square the distance, take this as R, from the source. This can be shown as 1/R².
When light travels through a medium and into another some of the energy is passed on while some is reflected. Light that is reflected from a flat boundary, a calm lake, will form a clear mirror image of the surroundings.
Specular Reflection
When the rays of light are hit a plane mirror and the reflected and incident rays are reflected at equal angles we call this reflection Specular.
source - http://s1.hubimg.com/u/4446928_f520.jpg
The angles that are reflected are called the angle of incidence and the angle of reflection.
Diffuse Reflection
Rough and uneven surfaces will reflect in different directions and it is these array of reflections that is called a Diffuse reflection.
source - the lecture slides
Diffuse reflected light is scattered and reflected in many different directions and it doesn't show any highlights or image like the previous Specular reflection. An example would be a light reflection off of a piece white paper.
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