The Crookes radiometer, also known as a light mill, is an airtight glass bulb containing a partial vacuum with a set of vanes mounted on a spindle inside that rotate when exposed to light, spinning faster under more intense light and so providing a rough measure of electromagnetic radiation intensity. It was invented in 1873 by the chemist William Crookes, who noticed that weighings in a partially evacuated chamber were disturbed when sunlight fell on the balance and investigated the effect further. The cause of its rotation was debated for years until an explanation was published in 1879, and the device is now used mainly in physics education as a demonstration of a heat engine driven by light energy.
Facts
Technology TypeLight-driven rotational radiometer 1 Invented YearCrookes initially misattributed the rotation to radiation pressure; the currently accepted thermal explanation was not published until 1879. Classification
MaturityTRL 3: Experimental Proof of Concept 1 Sources
1. Wikipedia: Crookes radiometer
WikipediaIntroduction, second paragraphQuote, Introduction, second paragraph
It was invented in 1873 by the chemist Sir William Crookes as the by-product of some chemical research.
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