radiometer
Americannoun
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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.
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an instrument for detecting and measuring small amounts of radiant energy.
noun
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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.
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Also called light mill
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The findings come from Juno's microwave radiometer, an instrument that has been studying Jupiter's atmosphere since the spacecraft entered orbit around the giant planet in 2016.
From Science Daily • May 21, 2026
Britain also supplied the radiometer, from Thales Alenia Space UK, and the imager, from Surrey Satellite Technology Ltd.
From BBC • May 28, 2024
The instrument, a mini microwave radiometer, can measure heat and light emanating from oxygen and water vapor in the air.
From The Verge • Jun. 10, 2022
Juno is equipped with a microwave radiometer, a device that tunes in to Jupiter’s microwave transmissions at six distinct frequencies, each value corresponding to a different depth.
From Scientific American • Oct. 28, 2021
In an atmosphere of ordinary density, the accession of heat which the vanes of a radiometer might receive from a radiant source would be diffused through the mass of the inclosed air.
From Scientific Culture, and Other Essays Second Edition; with Additions by Cooke, Josiah Parsons
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
