What does radiometer mean?
A radiometer is an instrument that detects or measures radiant energy, particularly electromagnetic radiation. Such instruments can indicate the presence of radiation, compare the intensity of radiation from different sources, or support specialized measurements in laboratories, medicine, astronomy, and industry. The best-known example is the Crookes radiometer, a sealed glass vessel containing a partial vacuum and a small rotor with polished or blackened vanes. It rotates when exposed to light and is often used as an elegant demonstration of radiation and thermal behavior. Despite its dramatic appearance, the rotor does not move simply because photons push on it; unequal heating of the vanes and the surrounding gas produces the principal force. Consequently, the word can refer both to a general radiation-measuring instrument and to this particular mechanically responsive device. It is therefore closely associated with scientific demonstration and measurement rather than everyday speech.
nounAn instrument for detecting or measuring radiant energy, especially electromagnetic radiation. The term is also associated with the Crookes radiometer, a light-powered device whose vanes rotate when exposed to a suitable light source.
- An instrument that detects or measures radiant energy, especially ionizing electromagnetic radiation.
- A radiation-sensitive instrument with moving vanes, most famously the Crookes radiometer or light mill.
"The laboratory used a radiometer to check whether the samples were emitting significant levels of radiation."
"A calibrated radiometer was mounted beside the detector to measure the intensity of the radiation beam."
"During the science lesson, the teacher placed a Crookes radiometer in a glass bulb and showed how its vanes turned in the light."
The plural is formed by adding -s to the singular noun.
"Several radiometers were positioned around the chamber."
The famous Crookes radiometer seems to spin because light exerts pressure, but its motion is driven mainly by a temperature difference between its faces.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of radiometer
Radiometer is a compound formed from radi-, associated with rays or radiation, and the measuring suffix -meter. Its elements ultimately derive from Latin radius, meaning “ray,” and Greek metron, meaning “measure.” The modern term was applied during the nineteenth century to instruments associated with radiation, and it later became strongly identified with the Crookes device.
Related word forms
How radiometer is actually used
The term is chiefly scientific and technical. General references to the Crookes radiometer often describe it as a light mill, while radiation monitoring and dosimetry usually require more specific terminology.