Léon Foucault
Jean Bernard Léon Foucault (UK: /ʒɒ̃ ˈbɛərnɑːr ˌleɪɒ̃ ˈfuːkoʊ/, US: /ˌʒɒ̃ bɛərˈnɑːr leɪˌɒ̃ fuːˈkoʊ/; French: [ʒɑ̃ bɛʁnaʁ leɔ̃ fuko]; 18 September 1819 – 11 February 1868) was a French physicist best known for his demonstration of the Foucault pendulum, a device demonstrating the effect of Earth's rotation. He also made an early measurement of the speed of light, discovered eddy currents, and is credited with naming the gyroscope.
Léon Foucault
Copley Medal (1855)
FRS (1864)
Early years[edit]
The son of a publisher, Foucault was born in Paris on 18 September 1819. After an education received chiefly at home, he studied medicine, which he abandoned in favour of physics due to a blood phobia.[1] He first directed his attention to the improvement of Louis Daguerre's photographic processes. For three years he was experimental assistant to Alfred Donné (1801–1878) in his course of lectures on microscopic anatomy.[2]
With Hippolyte Fizeau he carried out a series of investigations on the intensity of the light of the sun, as compared with that of carbon in the arc lamp, and of lime in the flame of the oxyhydrogen blowpipe; on the interference of infrared radiation, and of light rays differing greatly in lengths of path; and on the chromatic polarization of light.[2]
In 1849, Foucault experimentally demonstrated that absorption and emission lines appearing at the same wavelength are both due to the same material, with the difference between the two originating from the temperature of the light source.[3][4]
Later years[edit]
In 1862 Foucault was made a member of the Bureau des Longitudes and an officer of the Legion of Honour. He became a member of the Royal Society of London in 1864, and member of the mechanical section of the Institute a year later. In 1865 he published his papers on a modification of James Watt's centrifugal governor; he had for some time been experimenting with a view to making its period of revolution constant and developing a new apparatus for regulating the electric light. Foucault showed how, by the deposition of a transparently thin film of silver on the outer side of the object glass of a telescope, the sun could be viewed without injuring the eye. His chief scientific papers are to be found in the Comptes Rendus, 1847–1869.[10] Near his death he returned to Roman Catholicism that he previously abandoned.[11]
Collected Works: