diffraction grating

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dif·frac·tion grat·ing

(di-frak'shŭn grāt'ing),
A variety of filter composed of lined grooves in a thin layer of aluminum-copper alloy on a glass surface; used in spectrophotometers to disperse light into a spectrum. See: monochromator.

diffraction grating

The device in a spectrophotometer that disperses white light into the colors (wavelengths) of the electromagnetic spectrum, using multiple lines precisely etched into an optically aligned material such as a specialized mirror or metal plate.


Deviation of the direction of propagation of a beam of light, which occurs when the light passes the edge of an obstacle such as a diaphragm, the pupil of the eye or a spectacle frame. There are two consequences of this phenomenon. First, the image of a point source cannot be a point image but a diffraction pattern. This pattern depends upon the shape and size of the diaphragm as well as the wavelength of light. Second, a system of close, parallel and equidistant grooves, slits or lines ruled on a polished surface can produce a light spectrum by diffraction. This is called a diffraction grating. See Airy's disc; diffraction fringes; Maurice's theory.