Saturday, 10 May 2014
This slow learner, WHO COULDN'T READ UNTIL HE WAS 8; enabled the LIGHTHOUSE TO GUIDE SHIPS AT LONGER DISTANCES!!!
Augustin-Jean Fresnel (1788–1827), was a French engineer and physicist who contributed significantly to the establishment of the theory of wave optics. Fresnel studied the behaviour of light both theoretically and experimentally. He is perhaps best known as the inventor of the Fresnel lens, first adopted inlighthouses while he was a French commissioner of lighthouses, and found in many applications today. His Fresnel equations on waves and reflectivity also form the basis for many applications in computer graphics today - for instance, the rendering of water.
Fresnel was the son of an architect, born at Broglie (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-Vilaine; but having supported the Bourbons in 1814 he lost his appointment on Napoleon's return to power.
In 1815, on the second restoration of the monarchy, he obtained a post as engineer in Paris, where he spent much of his life from that time onwards. He appears to have begun his research in optics around 1814, when he prepared a paper on the aberration of light, although it was never published. In 1818 he wrote a memoir on diffraction, for which he received the prize of the Académie des Sciences at Paris in the ensuing year. He was the first to construct a special type of lens, now called a Fresnel lens, as a substitute for mirrors in lighthouses.
In 1819, he was nominated to be a commissioner of lighthouses. In 1823 he was unanimously elected a member of the academy, and in 1825 he became a member of the Royal Society of London. In 1827, the time of his last illness, the Royal Society of London awarded him the Rumford Medal. Fresnel died of tuberculosis at Ville-d'Avray, near Paris. He received only scant public recognition during his lifetime for his labours in the cause of optical science. Some of his papers were not printed by the Académie des Sciences until many years after his death.
But as he wrote to Young in 1824: in himself "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". His name is one of the 72 names inscribed on the Eiffel Tower.
His discoveries and mathematical deductions, building on experimental work by Thomas Young, extended the wave theory of light to a large class of optical phenomena, especially, to thedouble-refraction property of Iceland Spar, or calcite. In 1817, Young had proposed a small transverse component to light, while yet retaining a far larger longitudinal component.
A Fresnel lens is a type of compact lens originally developed by French physicist Augustin-Jean Fresnel for lighthouses. The design allows the construction of lenses of large aperture and short focal length without the mass and volume of material that would be required by a lens of conventional design. A Fresnel lens can be made much thinner than a comparable conventional lens, in some cases taking the form of a flat sheet. A Fresnel lens can capture more oblique light from a light source, thus allowing the light from a lighthouse equipped with one to be visible over greater distances.