A polychromator is an optical device that is used to disperse

light Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...

into different directions to isolate parts of the

spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...

of the light. A

prism PRISM is a code name for a program under which the United States National Security Agency (NSA) collects internet communications from various U.S. internet companies. The program is also known by the SIGAD . PRISM collects stored internet ...

diffraction grating In optics, a diffraction grating is an optical grating with a periodic structure that diffraction, diffracts light, or another type of electromagnetic radiation, into several beams traveling in different directions (i.e., different diffractio ...

can be used to disperse the light. Unlike a

monochromator A monochromator is an optics, optical device that transmits a mechanically selectable narrow band of wavelengths of light or other radiation chosen from a wider range of wavelengths available at the input. The name is . Uses A device that can ...

, it outputs multiple beams over a range of

wavelength In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase (waves ...

s simultaneously. Monochromators have one exit slit and one wavelength at a time can pass through that slit. Polychromators have multiple exit slits, each of which allows a different wavelength to pass through it. A detector is placed after each slit so that the light at each wavelength is measured by a different detector. Polychromators are often used in

spectroscopy Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Spectro ...

Spectrograph An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify mate ...

is a closely related term. Spectrographs generally do not make use of exit slits. Instead, they use a single spatially selective detector (such as photographic film or a

charge-coupled device A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...

). Spectrographs are generally used to observe a continuous range of wavelengths, while polychromators are more commonly used to observe several discrete wavelengths, leaving gaps in-between.

External links

* Palmer, Christopher, ''Diffraction Grating Handbook'', 8th edition, MKS Newport (2020)

Optical devices {{optics-stub