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
Other Word Forms
Etymology
Origin of radiometer
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.
Juno's microwave radiometer offered a better way to estimate the energy of lightning because microwave signals can pass through clouds.
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
With the radiometer, the Juno team can create heat maps of Jupiter’s atmospheric layers and look for circular features at different altitudes in the atmosphere, which indicate the presence of a vortex.
From Scientific American • Oct. 28, 2021
The spectroscope and the radiometer are more wonderful than any ‘supernatural’ thing yet heard of.
From British Goblins Welsh Folk-lore, Fairy Mythology, Legends and Traditions by Sikes, Wirt
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.
