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Augustin-Jean Fresnel (pronounced fray-NELL) (May 10, 1788 – July 14, 1827), was a French physicist who contributed significantly to the establishment of the wave theory of light and optics. Fresnel studied the behaviour of light both theoretically and experimentally.
Fresnel was the son of an architect, born at Brogue (Eure). His early progress in learning was slow, and he still could not read when he was eight years old. At thirteen he entered the École Centrale in Caen, and at sixteen and a half the École Polytechnique, where he acquitted himself with distinction. From there he went to the École des Ponts et Chaussées. He served as an engineer successively in the departments of Vendée, Drôme and Ille-et-Villaine; but having supported the Bourbons in 1814 he lost his appointment on Napoleon's return to power. On the second restoration of the monarchy, he obtained a post as engineer in Paris, where much of his life from that time was spent. His researches in optics, continued until his death, appear to have been begun about the year 1814, when he prepared a paper on the aberration of light, which, however, was not published. In 1818 he read a memoir on diffraction for which in the ensuing year he received the prize of the Académie des Sciences at Paris. He was in 1823 unanimously elected a member of the academy, and in 1825 he became a member of the Royal Society of London, which in 1827, at the time of his last illness, awarded him the Rumford Medal. In 1819 he was nominated a commissioner of lighthouses, for which he was the first to construct compound lenses as substitutes for mirrors. He died of tuberculosis at Ville-d'Avray, near Paris.
The undulatory theory of light, first founded upon experimental demonstration by Thomas Young, was extended to a large class of optical phenomena, and permanently established by his brilliant discoveries and mathematical deductions. By the use of two plane mirrors of metal, forming with each other an angle of nearly 180°, he avoided the diffraction caused in the experiment of F. M. Grimaldi on interference by the employment of apertures for the transmission of the light, and was thus enabled in the most conclusive manner to account for the phenomena of interference in accordance with the undulatory theory. With Francois Arago he studied the laws of the interference of polarized rays. Circularly polarized light he obtained by means of a rhombus of glass, known as "Fresnel's rhomb", having obtuse angles of 126° and acute angles of 54°. His labours in the cause of optical science received during his lifetime only scant public recognition, and some of his papers were not printed by the Académie des Sciences till many years after his decease. But, as he wrote to Young in 1824, in him "that sensibility, or that vanity, which people call love of glory" had been blunted. "All the compliments," he says, "that I have received from Arago, Laplace and Biot never gave me so much pleasure as the discovery of a theoretic truth, or the confirmation of a calculation by experiment."
This article incorporates text from the public domain 1911 Encyclopædia Britannica.
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