How are rainbows formed. I know it’s about refraction from water droplets, but shouldn’t you see many tiny rainbows instead of one big one.
In: Physics
Here’s an explanation I’ve stolen from *The Science of Discworld IV* by ian Stewart and Jack Cohen (and Terry Pratchett):
> Sunlight striking each drop gets refracted (and broken up into different colours) and then it bounces (total internal reflection) and passes out back towards the Sun, the different colours being further separated. Some fancy geometry shows that there is a focusing effect, because rays that enter the drop behave differently according to where they hit. Most of the light of a given colour comes out in a concentrated ‘beam’ at an angle of about 67˚ from the direction it went in. This angle depends on the wavelength, that is, the colour, of the light. So, if you’re standing with the Sun behind you, you see the backward-pointing coloured spray of rays from those raindrops that form a 67˚ circle in the sky. Someone standing a metre to your right doesn’t see your raindrops, but those corresponding to a different circle a metre to the right of yours.
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