#diffraction_grating__diffractiongrating__grating  optical device consisting of a surface with many parallel grooves in it; disperses a beam of light (or other electromagnetic radiation) into its wavelengths to produce its spectrum
  supertype:  optical_device__opticaldevice  a device for producing or controlling light
  subtype:  echelon  a diffraction grating consisting of a pile of plates of equal thickness arranged stepwise with a constant offset

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