Why are there rainbows?

What is light?

• Light is a wave characterized by its wavelength and frequency.
• Red light is low frequency, yellow is higher and blue is higher still
• for visible light : ROYGBIV

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White light is really composed of a mixture of all of the visible colors of light. Something about a rainbow treats the different frequencies differently and so that the white light is "broken up" into individual colors.

Speed and direction of light in materials?

• In a vacuum all frequencies of light travel at the same speed but in a material, the speed is reduced.
• The ratio of the speed of light in a vacuum, c, to the speed of light in a material, v, is the index of refraction, n = c / v.
• n equals about 1.333 in water

• The change in speed causes the direction of a light beam to change.
There is a relationship between the angles at which light enters and leaves a boundary between materials with different indices of refraction called Snell's law.
 n1 * sin (theta1) = n2 * sin (theta2)  Snell's Law
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