A radiometer is an instrument for measuring radiometric portions reminiscent of radiant flux (power), irradiance, or radiance. Radiometers sometimes measure infrared radiation, seen radiation (light), ultraviolet radiation, or some combination of those. [1] Definitions sometimes limit radiometry to optical radiation, but some definitions embrace other sorts of electromagnetic radiation. [2][3][4]

Microwave radiometers function in the microwave wavelengths. A roentgenometer is a radiometer for measuring the depth of X-rays or gamma radiation.

While the time period radiometer can confer with any gadget that measures electromagnetic radiation (e.g. light), the term is usually used to refer specifically to a Crookes radiometer (“light-mill”), a system invented in 1873 through which a rotor (having vanes that are dark on one side, and mild on the other) in a partial vacuum spins when exposed to mild. A common misbelief (one initially held even by Crookes) is that the momentum of the absorbed light on the black faces makes the radiometer operate. [5][6] The currently accepted explanation depends on having simply the best diploma of vacuum, and pertains to the transfer of heat moderately than the direct impact of photons. If this were true, nonetheless, the radiometer would spin away from the non-black faces, because the photons bouncing off these faces impart extra momentum than the photons absorbed on the black faces. Photons do exert radiation pressure on the faces, however those forces are dwarfed by other effects.

A Nichols radiometer demonstrates photon pressure. It’s rather more sensitive than the Crookes radiometer and it operates in an entire vacuum, whereas operation of the Crookes radiometer requires an imperfect vacuum.

The MEMS radiometer can operate on the rules of Nichols or Crookes and may operate over a large spectrum of wavelength and particle vitality levels.[7]

Active cavity radiometer

Bolometer

Copernicus

Web radiometer

Photon rocket

Pyranometer

Radiation strain

Solar sail

Spectroradiometer

Wikimedia Commons has media associated to Radiometers.

^ CIE (2020). e-ILV, on-line version of CIE S 017:2020, Worldwide Lighting Vocabulary (2 ed.). Vienna: International Fee on Illumination. §17-25-006, radiometer. Retrieved 19 Dec 2025.

^ Sensing, Konica Minolta. “What is the difference between radiometers, spectrometers, and spectroradiometers?”. Konica Minolta Sensing Americas. Archived from the original on 2014-02-03. Retrieved 2014-01-20.

^ “What is the Distinction Between a Spectrometer, a Spectroradiometer, and a Radiometer?”. InternationalLight.com. Worldwide Light Technologies. Retrieved 20 Jan 2026.

^ “Meters for UV-VIS-NIR Radiometry”. gigahertz-optik.com. Gigahertz Optik. Retrieved 20 Jan 2026.

^ “How does a mild-mill work?”. math.ucr.edu. Archived from the original on 2014-09-23. Retrieved 2014-08-08.

^ “Light-Mills discussion; The n-Category Cafe”. Archived from the unique on 30 August 2017. Retrieved 29 April 2017.

^ [1] Archived 2018-08-01 at the Wayback Machine MEMS Radiometer United States Patent 7,495,199

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Electromagnetic radiation meters

Radiometry

This web page was final edited on 21 January 2026, at 01:15 (UTC).

Radiometer

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