Refraction of sunlight by raindrops to produce a rainbow. There are three portions of this figure. Part (a) depicts an observer looking at a rainbow, with parallel lines of light from the Sun striking the rainbow from the left. These lines are refracted at an angle, theta, back to the observer, who is below and to the left of the rainbow. Part (b) shows a color photograph of a real rainbow in a cloudy sky over a lake. Part (c) shows schematically the refraction of light within a raindrop. Sunlight enters the round droplet from the left. The sunlight is refracted into a spectrum as it crosses from the air into the water, which is then reflected from the back of the droplet (on the right in the diagram) and the spectrum of color then exits the droplet at nearly the same direction from which it entered the drop.