| a band of equidistant, parallel lines, usually more than 5000 per inch (2000 per centimeter), ruled on a glass or polished metal surface for diffracting light to produce optical spectra. |
| diffraction grating n. A usually glass or polished metal surface having a large number of very fine parallel grooves or slits and used to produce optical spectra by diffraction of reflected or transmitted light. |
| diffraction grating
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. |
diffraction grating
component of optical devices consisting of a surface ruled with close, equidistant, and parallel lines for the purpose of resolving light into spectra. A grating is said to be a transmission or reflection grating according to whether it is transparent or mirrored-that is, whether it is ruled on glass or on a thin metal film deposited on a glass blank. Reflection gratings are further classified as plane or concave, the latter being a spherical surface ruled with lines that are the projection of equidistant and parallel lines on an imaginary plane surface. The advantage of a concave grating over a plane grating is its ability to produce sharp spectral lines without the aid of lenses or additional mirrors. This makes it useful in the infrared and ultraviolet regions in which these radiations would otherwise be absorbed upon passage through a lens
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