RAINBOW EDGES IN A LENS
demonstrates a phenomenon that has always been a problem for astronomers
and camera makers—the tendency of lenses to make rainbows out
of white light. This defect in lenses is called "chromatic
aberration" and occurs because the edges of a lens are prism
shaped and, like a prism, disperse the colors in white light. Blue
light is bent most and therefore focuses closer to the lens than
red light.
