An old engraving of an infrared ‘dark box’. It is from a Victorian book of the 1880s. Humphry Davy developed the first the first practical electric arc light in 1806. Two pieces of pure carbon have electricity from a powerful battery passed through them and an arc is created when the carbon burns, creating heat and light. Herschel discovered infrared light in 1880. John Tyndall (1820–1893) discovered the ‘Tyndall effect’ in air. Tyndall’s water-cooled dark box passes rays through a ‘ray filter’ filtering out the light. Any object held in the path of the ‘red light’ (infrared light) gets hot.
An old engraving of John Tyndall’s heat-producing ‘dark box’. It is from a Victorian mechanical engineering book of the 1880s. English chemist Humphry Davy developed the first incandescent light in 1802, followed by the first practical electric arc light in 1806. Two pieces of pure carbon have electricity from a powerful battery passed through them. By adjusting the gap between the carbon pieces, a point is found where an arc is created and the carbon burns – as well as creating intense heat, light is also emitted. Scientist Sir Frederick William Herschel, who notably discovered the planet Uranus in 1781, also discovered infrared light in 1880. John Tyndall (1820–1893) was a prominent 19th-century Irish physicist. He made discoveries in infrared radiation and the physical properties of air. The scattering of light by particulate impurities in air (and other gases and liquids) is known as the ‘Tyndall effect’ or ‘Tyndall scattering’. In Tyndall’s dark box apparatus passes rays through a ‘ray filter’ (an iodine solution) which intensified the heat by filtering out the light. The machine needed to be water cooled. Any object held in the path of the ‘red light’ (infrared light) would become hot.
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