radiometer

[ rey-dee-om-i-ter ]

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.

radiometer

/ ˌreɪdɪˈɒmɪtə; ˌreɪdɪəʊˈmɛtrɪk /

noun

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

radiometer

/ 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

Derived Forms

• ˌradiˈometry, noun
• radiometric, adjective

Other Words From

• ra·di·o·met·ric [rey-dee-oh-, me, -trik], adjective
• radi·ome·try noun

Word History and Origins

Origin of radiometer¹

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

Example Sentences

Thus it appears that we have been able to show by very definite experimental evidence that the radiometer is a heat engine.

From Project Gutenberg

Another illustration of the power of cooled charcoal to produce high vacua is afforded by a Crookes radiometer.

From Project Gutenberg

To a radiometer (fig. 6) with attached charcoal bulb B was sealed a tube ending in a small bulb A containing a globule of mercury.

From Project Gutenberg

Count Bathyani recently took up a radiometer to a height of about a mile.

From Project Gutenberg

The monitors were synchronized with the radiometer and changed view at every ten-mile marker.

From Project Gutenberg