radiometric /ray'dee oh me"trik/, adj.radiometry, n.
/ray'dee om"i teuhr/, n.
1. Also called Crookes radiometer. an instrument for demonstrating the transformation of radiant energy into mechanical work, consisting of an exhausted glass vessel containing vanes that revolve about an axis when exposed to light.
2. an instrument for detecting and measuring small amounts of radiant energy.
[1870-75; RADIO- + -METER]

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      instrument for detecting or measuring radiant energy. The term is applied in particular to devices used to measure infrared radiation. Radiometers are of various types that differ in their method of measurement or detection. Those that function by means of an increase in the temperature of the device, such as Herschel's thermometer, are called thermal detectors. Commonly used thermal detectors include the thermocouple, which produces a voltage when heated, and the bolometer, which undergoes a change in electrical resistance when heated. Devices that can, in principle, detect a singular quantum of radiant energy, such as Becquerel's photographic plate, are called quantum detectors. The photoelectric cell is the basis of many current quantum detectors.

      The term radiometer is often used to refer specifically to a type of detector invented by Sir William Crookes in the late 1800s. It is rarely used as a scientific instrument, because it was found to be insensitive and not easily calibrated, but it paved the way for the more exact instruments in use today. A Crookes radiometer consists of a glass bulb from which most of the air has been removed, thereby creating a partial vacuum, and a rotor that is mounted on a vertical support inside the bulb. The rotor bears four light, horizontal arms mounted at right angles to one another on a central pivot; the rotor can turn freely in the horizontal plane. At the outer end of each arm is mounted a vertical metal vane. Each vane has one side polished and the other side blackened; the vanes are arranged so that the polished side of one faces the blackened side of the next. When radiant energy strikes the polished surfaces, most of it is reflected away, but when it strikes the blackened surface, most of it is absorbed, raising the temperature of those surfaces. The air near a blackened surface is thus heated and exerts a pressure on the blackened surface, causing the rotor to turn.

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Universalium. 2010.

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Look at other dictionaries:

  • Radiomēter — (Strahlungsmesser, Lichtmühle), ein von Crookes 1874 erfundener Apparat, besteht aus einem vierarmigen Rädchen (s. Figur), das mittels eines Glashütchens auf einer Nadelspitze leicht drehbar ausgesetzt ist. Jeder der aus Platindraht verfertigten… …   Meyers Großes Konversations-Lexikon

  • Radiometer — Ra di*om e*ter (r[=a] d[i^]*[o^]m [ e]*t[ e]r), n. [L. radius radius + meter: cf. F. radiom[ e]tre.] 1. (Naut.) A forestaff. [1913 Webster] 2. (Physics) An instrument designed for measuring the mechanical effect of radiant energy. [1913 Webster]… …   The Collaborative International Dictionary of English

  • Radiometer — Radiometer, so v.w. Jakobsstab 2) …   Pierer's Universal-Lexikon

  • Radiometer — (Lichtmühle, Strahlungsmesser), ein von Crookes 1874 erfundener Apparat. Eine stark evakuierte Glaskugel enthält über einer senkrechten Nadel als Achse mittels eines Glashütchens aufgehängt ein Aluminiumkreuz mit Glimmer oder Aluminiumblättchen… …   Lexikon der gesamten Technik

  • Radiometer — Radiomēter (lat. grch.), Lichtmühle, von Crookes 1874 erfundener physik. Apparat, der durch die Einwirkung von Licht und Wärmestrahlen in Bewegung gesetzt wird. Tatsächlich wirken nur (im Licht enthaltene) Wärmestrahlen. Ein in einem luftleeren… …   Kleines Konversations-Lexikon

  • Radiometer — Radiometer, lat. griech., Gradbogen, Polhöhemesser …   Herders Conversations-Lexikon

  • Radiometer — См. Радиометр Термины атомной энергетики. Концерн Росэнергоатом, 2010 …   Термины атомной энергетики

  • radiometer — [rā΄dē äm′ə tər] n. [ RADIO + METER] 1. a device containing a set of vanes that are blackened on one side and suspended on an axis in a vacuum: the vanes rotate on exposure to sunlight 2. an instrument for measuring radiant energy in any part of… …   English World dictionary

  • Radiometer — A radiometer is a device for measuring the radiant flux (power) of electromagnetic radiation. Generally, the term “radiometer” denotes an infrared radiation detector, yet it also comprises detectors operating on any electromagnetic wavelength,… …   Wikipedia

  • Radiometer — Ein Radiometer ist ein Detektor zur Messung der Bestrahlungsstärke. Der Begriff Radiometer wird jedoch nicht nur für ein Funktionsprinzip verwendet. Die von William Crookes erfundene Lichtmühle – ein sich bei Beleuchtung drehendes Flügelrad –… …   Deutsch Wikipedia

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