ROYAL ASTRONOMICAL SOCIETY / SCIENCE PHOTO LIBRARY ROYAL ASTRONOMICAL SOCIETY / SCIENCE PHOTO LIBRARY
Herschel infrared light experiments, artwork. In 1800, the British astronomer William Herschel (1738-1822) carried out a series of experiments that led to his discovery of infrared light. Here, sunlight was split into its colours by refraction in a prism, passed through a slit in a shade, and allowed to heat three thermometers. Adjusting the shade allowed the heating effects of different colours to be investigated. The hottest area, beyond visible red light, became known as infrared radiation. This illustration (plate X) accompanied the first of Herschel's four papers on this topic (read 27 March 1800), published in volume 90 of 'Philosophical Transactions' (Royal Society of London).
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