Rainbow Edges

Rainbow Edges 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. In part one of this two-part exhibit, the visitor can see the fuzzy rainbows around lights caused by the lens in his or her own eye. By looking at the purple H, the visitor sees either sharp red dots surrounded by fuzzy blue halos, or blue dots with red halos. The eye’s lens bends more blue light than red, so it can’t focus both colors on the retina at the same time. Normally, inhibition eliminates these rainbows from view, but because red and blue are at opposite ends of the spectrum, they are too far apart to inhibit each other. Observable also is the chromatic aberration of a lens. A colorless screen of dots, seen through the lens, produces colored spots. The lens bends different wave-lengths of light at slightly different angles, which accounts for the rainbow effect.