What is the science behind the formation of rainbow?
Snell’s law causes the different frequencies of light to be refracted differently as the light passes through one of the many water molecules in the sky. The picture in the link below with the caption “White light separates into different colors” does a good job of showing how this works. The red light (at one end of the spectrum) is refracted less than blue light (at the other end of the spectrum). Other colors are refracted by some intermediate amount. Once the colors come out, they come back towards the general direction of the sun, which is why you have to look away from the sun to see the rainbow. Also, the rainbow leaves the water droplet at an angle of 40 to 42 degrees. In the antique picture further down with the caption “Rene Descartes sketch”, you see that the angle between sun-to-droplet and droplet-to-person, equals the angle between droplet-to-person and person-to-horizon (because they are “alternate interior angles” from geometry), which means the rainbow is always in a r