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[rey-dee-om-i-ter] /ˌreɪ diˈɒm ɪ tər/
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.
an instrument for detecting and measuring small amounts of radiant energy.
Origin of radiometer
First recorded in 1870-75; radio- + -meter
Related forms
[rey-dee-oh-me-trik] /ˌreɪ di oʊˈmɛ trɪk/ (Show IPA),
radiometry, noun Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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British Dictionary definitions for radiometric


any instrument for the detection or measurement of radiant energy
Derived Forms
radiometric (ˌreɪdɪəʊˈmɛtrɪk) adjective
radiometry, noun
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for radiometric

1877, from radiometer "instrument to transform radiant energy into mechanical work" (1875), radiometry, from radio-, here indicating "radiant energy," + -metric. Radiometric dating attested from 1906.

Online Etymology Dictionary, © 2010 Douglas Harper
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radiometric in Medicine

radiometer ra·di·om·e·ter (rā'dē-ŏm'ĭ-tər)

  1. A device that measures the intensity of radiant energy, consisting of a partially evacuated glass bulb containing lightweight vertical vanes, each blackened on one side, suspended radially about a central vertical axis to permit their revolution about the axis as a result of incident radiation.

  2. An instrument that detects electromagnetic radiation.

  3. A device for determining the penetrative power of x-rays.

ra'di·om'e·try (-trē) n.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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radiometric in Science
A device used to detect or measure radiation. Radiometers generally consist of a glass bulb containing a rarefied gas in which four diamond-shaped paddles are mounted on a central axis. Each paddle is black on one side and silvery on the other. When radiation such as sunlight strikes them, the black side absorbs radiation and the silvery side reflects it, resulting in a temperature difference between the two sides and causing motion of gas molecules around the edges of the paddles. This motion of the surrounding gas molecules causes the paddles to spin. Precision radiometers, which use a complete vacuum rather than a gas, exploit the difference in radiation pressure on either side of the paddles to cause them to spin. Radiometers measure the intensity of radiation by measuring the rate of spin of the paddles. Also called light mill.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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