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Q & A: rainbow

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Most recent answer: 10/22/2007
Why does a rainbow bend? A friend of mine says that it is because each colour has different wave lengths. I have no idea wat this means. My theory is that a rainbow has to be a certain distance from the eye at all times and at all angles. so the eye becomes a radius. But ,as my friend told me, that does not explain why a rainbow bends on film.
- Steven Groves (age 15)
Your friend is correct in that different colors have different wavelengths.   You are correct in that all points around the rainbow's arc have the same angle with respect to the sun.  Minor corrections due to the different wavelengths having different indices of refraction then tend to spread out the colors. 

The details are a bit complicated.  I recommend looking at the excellent article in Wickipedia.

Lee H

(published on 10/22/2007)

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