|a glass plate or a mirror with a large number of equidistant parallel lines or grooves on its surface. It causes diffraction of transmitted or reflected light, ultraviolet radiation, or X-rays|
A barrier consisting of alternately transparent and opaque stripes, through which radiation such as light is passed and projected onto a screen or other detection device. The interference patterns cast by the diffraction grating on the screen or detector can be analyzed to determine the frequency of the radiation. See also interferometer.