81:("light-mill"), a device invented in 1873 in which a rotor (having vanes which are dark on one side, and light on the other) in a partial vacuum spins when exposed to light. A common misbelief (one originally held even by Crookes) is that the momentum of the absorbed light on the black faces makes the radiometer operate. If this were true, however, the radiometer would spin away from the non-black faces, since the photons bouncing off those faces impart more momentum than the photons absorbed on the black faces. Photons do exert radiation pressure on the faces, but those forces are dwarfed by other effects. The currently accepted explanation depends on having just the right degree of vacuum, and relates to the transfer of heat rather than the direct effect of photons.
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demonstrates photon pressure. It is much more sensitive than the
Crookes radiometer and it operates in a complete vacuum, whereas operation of the Crookes radiometer requires an imperfect vacuum.
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radiometer can operate on the principles of
Nichols or Crookes and can operate over a wide spectrum of wavelength and particle energy levels.
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can refer to any device that measures electromagnetic radiation (e.g. light), the term is often used to refer specifically to a
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Device for measuring the radiant flux (power) of electromagnetic radiation
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For the specific radiometer that this term often refers to, see
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262:MEMS Radiometer United States Patent 7,495,199
229:"Light-Mills discussion; The n-Category Cafe"
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279:Electromagnetic radiation meters
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175:Konica Minolta Sensing Americas
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46:is a device for measuring the
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200:"How does a light-mill work?"
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169:Sensing, Konica Minolta.
52:electromagnetic radiation
105:Active cavity radiometer
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64:Microwave radiometers
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135:Radiation pressure
86:Nichols radiometer
79:Crookes radiometer
56:infrared radiation
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21:Crookes radiometer
150:Spectroradiometer
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30:An example of a
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237:. Retrieved
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48:radiant flux
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130:Pyranometer
60:ultraviolet
50:(power) of
284:Radiometry
273:Categories
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185:2014-01-20
156:References
145:Solar sail
140:Radiometry
115:Copernicus
75:radiometer
62:detector.
40:radiometer
110:Bolometer
68:microwave
256:Archived
239:29 April
233:Archived
208:Archived
179:Archived
99:See also
241:2017
93:MEMS
91:The
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