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Foucault was the son of a publisher at Paris, where he was born on September 18, 1819. After an education received chiefly at home, he studied medicine, which, however, he speedily abandoned for physical science. He first directed his attention to the improvement of L. J. M. Daguerre's photographic processes. For three years he was experimental assistant to Alfred Donné ( 1801— 1878) in his course of lectures on microscopic anatomy.
With A. H. L. Fizeau he carried on a series of investigations on the intensity of the lightLight is electromagnetic radiation with a wavelength that is visible to the eye, or in a more general sense, any electromagnetic radiation in the range from infrared to ultraviolet. The three basic dimensions of light (and of all electromagnetic radiation of the sunThe Sun (also called Sol is the star in our solar system. Planet Earth orbits the Sun. Other bodies that orbit the Sun include other planets, asteroids, meteoroids, comets and dust. Not all objects passing through the solar system have been orbitally capt, as compared with that of carbonAlternative meaning: Carbon (computing Carbon is a chemical element in the periodic table that has the symbol C and atomic number 6. An abundant nonmetallic, tetravalent element, carbon has several allotropic forms: diamonds (hardest known mineral). Bindi in the arc lampAn arc lamp is a device that produces light by the sparking (or arcing, from voltaic arc) of a high current between two carbon rod electrodes. The rods are touched and then slowly drawn apart; as the rods separate the current is "struck" and arcs across t, and of limeProperties General Name Calcium oxide Chemical formula Ca O Appearance White solid Physical Formula weight 56. 1 amu Melting point 3200 K (2927 °C) Boiling point 3773 K (3500 °C) Density 3. 3 ×103 kg/ m3 Crystal structure NaCl Solubility hydrolysed Thermo 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 polarizationThis article treats polarization in electrodynamics. Other articles treat polarization in electrostatics, polarization in politics and polarization in psychology. In electrodynamics, polarization is a property of waves, such as light and other electromagn of light.
In the 1840s, he contributed to the Comptes Rendus a description of an electromagnetic regulator for the electric arc lamp, and, in conjunction with Henri Victor Regnault, a paper on binocular vision. In 1850, by the use of a revolving mirror similar to that used by Sir Charles Wheatstone for measuring the speed of electric currents, he was able to demonstrate the greater speed of light in air than in water, and to establish that the speed of light in different media is inversely as the refractive indices of the media (see Fizeau-Foucault Apparatus).
For his demonstration in 1851 of the diurnal motion of the Earth by the rotation of the plane of oscillation of a freely suspended, long and heavy pendulum exhibited by him at the Panthéon in Paris, and again in the following year by means of his invention the gyroscope, he received the Copley medal of the Royal Society in 1855, and in the same year he was made physical assistant in the imperial observatory at Paris.
In September of that year he discovered that the force required for the rotation of a copper disc becomes greater when it is made to rotate with its rim between the poles of a magnet, the disc at the same time becoming heated by the eddy current or "Foucault currents" induced in the metal.
Foucault invented in 1857 the polarizer which bears his name, and in the succeeding year devised a method of giving to the mirror of reflecting telescopes the shape of a spheroid or a paraboloid of revolution. With Wheatstone’s revolving mirror he in 1862 determined the speed of light to be 298,000 km/ s (about 185,000 mi./s) —10,000 km/s less than that obtained by previous experimenters and only 0.6% off the currently accepted value.