Somewhere Over The Rainbow...

The rain has just ended. The sun begins to peek a ray out from behind a cloud. There it is. The rainbow beams out from the gloom and mist that blankets the earth. How did this happen? Many would credit the gods for making such a beautiful sight, but the real creator is light itself.

Light is made up a many different colors. These colors all have different frequencies. The frequency, or speed, they posses make them appear different to us. Our eyes receive them differently and that is how colors are perceived. When all the colors come together they create white light. Because the individual colors travel at different speeds they can be separated. You can separate light using a different medium than air. Examples of this are glass and water. When a beam of light enters a piece of glass or a droplet of water the light slows down and is refracted, or broken apart. The degree to which it is broken is called the Index of Refraction. The change in speed causes the direction of the light beam to change as it passes from one material to another.

The Index of Refraction is calculated using the equation: n=c/v; where n equals the Index of Refraction, c equals the speed of light in a vacuum, and v equals the speed of light in the material being tested. The Index of Refraction in glass is 1.5 and in water it is 1.333.

The Index of Refraction value can be used in Snell's Law. This law states the relationship between the IOR and the Angle of Incidence, or angle at which the light exits the material. Snell's Law states: n1sin(theta1)=n2sin(theta2).


So, what does all this have to do with the creation of rainbows?? Rainbows form when there is a lot of water vapor in the air, especially after a rainstorm. When the sun comes back out the sun rays strike the water droplets in the air and the light is refracted. The Angle of Incidence to the rainbow is always 42 degrees. The light is broken up or separated and can be viewed as the beautiful rainbow that graces the sky after a rainstorm.


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Created by Casey Holzgartner 2/20/01