Radiometer

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A radiometer is a device used to measure the radiant flux or power in electromagnetic radiation. Although the term is perhaps most generally applied to a device which measures infrared radiation, it can also be applied to detectors operating any wavelength in the electromagnetic spectrum.

The radiation detector within a radiometer is most often a bolometer which absorbs the radiation falling on it and, as a result, rises in temperature. This rise can then be measured by a thermometer of some type. This temperature rise can be related to the power in the incident radiation.

An early detector of infrared and visible radiation (light) was the Crookes radiometer. A more sensitive device, employing a different principle, is the Nichols radiometer.

A Microwave radiometer operates in the Microwave region of the electromagnetic spectum.