radiometer

American  

[ray-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  

/ 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

• radiometry
  noun
• radiometric
  adjective

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Etymology

Origin of radiometer

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

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Example Sentences

See Examples For:

radiometer

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

And a radiometer will sense how much of the energy falling on to Earth from the Sun is being reflected or radiated back into space.

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

Sir William Crookes took up in 1872 the study of electric discharge through 192 high vacua, having been led to it by his researches on the radiometer.

From Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2 "Ehud" to "Electroscope" by Various

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