Atmospheric Optical Phenomena

The most remarkable phenomenon in the atmosphere is likely to be the rainbow. To understand how a rainbow is created, imagine a single beam of white light entering a spherical droplet of water. As the light passes from air into water, it undergoes refraction (that is, it is bent). However, each color present in the white light is bent by a different amount—the blues and violets more than the reds and yellows. The light is said to be dispersed, or separated according to color. After the dispersed rays pass into the water droplet, they reflect off the rear inner surface of the droplet and exit into the air once more. As the light rays pass out of the water into the air, they are refracted a second time. As a result of this second refraction, the separation of blues and violets from reds and yellows is made more distinct.

An observer on Earth's surface can see the net result of this sequence of events repeated over and over again by billions of individual water droplets. The rainbow that is produced consists simply of the white light of the sun separated into its component parts by each separate water droplet.