diffraction grating - definition - optics and sound

Definition: One of the most useful optical devices for producing spectra. In one of its forms, the diffraction grating consists of a flat glass plate in the surface of which has been ruled with a diamond, equidistant parallel straight lines which may be as close as 1000 per millimetre. If a narrow source of light is viewed through a grating, it is seen to be accompanied on each side by one or more spectra. These are produced by diffraction effects from the lines acting as a very large number of equally spaced parallel slits.