Editing Crookes radiometer (section)

===Origin of the name===
The [[prefix]] "[[Wikt:radio-|radio-]]" in the title originates from the combining form of Latin ''radius'', a ray: here it refers to [[electromagnetic radiation]]. A Crookes radiometer, consistent with the [[suffix]] "[[Wikt:-meter|-meter]]" in its title, can provide a quantitative measurement of electromagnetic radiation intensity. This can be done, for example, by visual means (e.g., a spinning slotted disk, which functions as a simple [[stroboscope]]) without interfering with the measurement itself.

Radiometers are now commonly sold worldwide as a novelty ornament; needing no batteries, but only light to get the vanes to turn. They come in various forms, such as the one pictured, and are often used in [[science museum]]s to illustrate "radiation pressure" &ndash; a scientific principle that they do not in fact demonstrate.