Rainbow

Rainbow, arch of concentric spectrally-colored rings seen in the sky by an observer looking at rain, mist, or spray with his or her back to the sun. The colors are produced by sunlight's being refracted and internally reflected by spherical droplets of water. The primary rainbow, with red on the outside and violet inside, results from one total internal reflection. Sometimes a dimmer secondary rainbow with reversed colors is seen, arising from a second total internal reflection.