Monochromators are optical techniques used to separate a specific range of wavelengths representing a single color. Czerny-Turner monochromators, one of the more commonly used designs, consists of a light source, two concave mirrors, and a plane diffraction grating.
As a thin beam of white light enters the monochromator from a light source, it falls onto the first mirror, allowing the light beam to run parallel.
These parallel beams are then split into different wavelengths by the plane grating, which is then reflected on to the second concave mirror. A thin exit slit then allows a specific wavelength to pass through for analytical purposes.