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.
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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.
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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).
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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.
"Try This At Home"
Water as a Lens
"How Do Bee's See?"
Credits:
Created by Casey Holzgartner 2/20/01
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