disperser

The term disperser (or dispersing element) refers to the part of a spectrometer that disperses incoming light by wavelength, i.e., directs the light differently according to its wavelength so that the spectrum is evident. Bending the light's direction according to wavelength to spread it out in such manner is termed dispersion, or more specifically, chromatic dispersion. Example dispersers are prisms, gratings, grisms, and Fabry-Pérot interferometers.