Monday, July 24, 2017

The discovery of infrared by Sir William Herschel

Like all bodies above absolute zero it radiates from its surface electromagnetic waves whose wavelengths and intensity are related to the absolute temperature and to the emissivity of its surface.

These waves were named by their discoverer, Sir William Herschel (1738-1822), infrared waves because they occurred beyond the red end of the visible spectrum. In 1800 Sir William Herschel, best known as the discoverer of the planet Uranus, carried out experiments to determine the distribution of heating power among the various colors which could be produced by passing the sun’s light through a prism.
Sir William Herschel (1738-1822)
Sir William arranged his apparatus so that the spectral colors were projected upon a table, and by means of mercury in glass thermometer he explored every part of the spectrum, measuring the relative rise in temperature produced.

He discovered that the heating power of the sun’s rays increased from the violet to the red end of the spectrum and that the maximum was not reached until the thermometer had been placed beyond the end of the visible red.

After this, the infrared thermography started to be used in human assessment and more specifically in medicine. It is possible to consider the 1970s as being the beginning of infrared thermography in sport science.
The discovery of infrared by Sir William Herschel
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