Overview

In a strange turn of events, diffraction gratings have become important in acoustics. The subject of diffraction gratings brings to mind several memories, widely separated in time and space.

There are three large Morpho butterflies mounted in a frame in our home, a sweet reminder of first seeing their gorgeous flashes of color as they flitted about in a jungle clearing in Panama. Their color changes in a most dazzling fashion. They were even more fascinating to me when I learned that this color is not pigmentation-it is structural color. The butterfly's wing is basically a tawdry tan-the vivid coloring is the result of breaking down the light that falls upon it into rainbow colors by diffraction. Viewed through a microscope, the wing surface is made up of a myriad of very small bumps and grooves.

At Mt. Wilson Observatory is the diffraction grating used by Edwin Hubble to measure the light of distant stars. Using this diffraction grating, he formulated his theory of the expanding universe based on the "red shifts" of starlight he observed. It is a glass plate with precise, parallel lines cut on it, many thousands to the inch. Sunlight falling on this grating is broken down into its component colors, just as the light from the stars.

In early days, the diffraction of X-rays by crystals was studied in the Physics Department at Stanford University in a safety cage made of chicken wire screen in a remote corner of the basement. Crystals ...