radiometer

American  

[rey-dee-om-i-ter] / ˌreɪ diˈɒm ɪ tər /

noun

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.

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radiometer British  

/ ˌreɪdɪəʊˈmɛtrɪk, ˌreɪdɪˈɒmɪtə /

noun

1. any instrument for the detection or measurement of radiant energy

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radiometer Scientific  

/ rā′dē-ŏm′ĭ-tər /

1. 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.

2. Also called light mill

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Other Word Forms

• radiometric adjective
• radiometry noun

Etymology

Origin of radiometer

First recorded in 1870–75; radio- + -meter

Example Sentences

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

The device they use is a microwave radiometer.

From Scientific American • Aug. 3, 2021

Every station except for the highest one is outfitted with a net radiometer, an instrument that measures incoming and outgoing radiation, and the lower stations also carry rain gauges and present weather sensors.

From Washington Post • Dec. 13, 2019

The moving part of the radiometer is a small horizontal wheel, to the ends of whose arms are fastened vertical vanes, usually of mica, and blackened on one side.

From Scientific Culture, and Other Essays Second Edition; with Additions by Cooke, Josiah Parsons