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Marie Alfred Cornu ( March 6, 1841— April 12, 1902) was a French physicist.

Cornu was born at Orléans, and after being educated at the Ecole Polytechnique and the Ecole des Mines, in 1867 he became professor of experimental physics in the former institution, where he remained throughout his life. Although he made various excursions into other branches of physical science, undertaking, for example, with Jean-Baptistin Baille about 1870 a repetition of Cavendish's experiment for determining the gravitational constant G, his original work was mainly concerned with opticsSee also list of optical topics. Optics is a branch of physics that describes the behavior and properties of light and the interaction of light with matter. Optics explains and is illuminated by optical phenomena. The field of optics usually describes the and spectroscopySpectroscopy is the study of spectra, ie. the dependence of a physical measure to frequency. Spectroscopy is often used in physical and analytical chemistry for the identification of substances, through the spectrum emitted or absorbed. A device for recor. In particular he carried out a classical redetermination of the speed of lightCherenkov effect in a "swimming pool" nuclear reactor. The effect is due to electrons moving faster than the speed at which light moves in water. The speed of light (denoted as c reputedly from the Latin celeritas "speed", and also known as Einstein's con by A. H. L. FizeauArmand Hippolyte Louis Fizeau Physicist Armand Hippolyte Louis Fizeau ( September 23, 1819- 1896), French physicist, was born in Paris. His earliest work was concerned with improvements in photographic processes; and then, in association with J. Foucault,'s method (see Fizeau-Foucault Apparatus), introducing various improvements in the apparatus, which added greatly to the accuracy of the results. This achievement won for him, in 1878Events January Cleopatra's Needle arrives in London January 9 Humbert I becomes King of Italy January 23 Disraeli orders British fleet to Dardanelles January 28 The Yale News becomes the first daily, college newspaper in the United States. January 31 Turk, the prix Lacaze and membership of the Academy of Sciences in France, and the Rumford MedalNot to be confused with the Rumford Prize In 1796, Benjamin Thompson, known as Count Rumford, gave $5000 separately to the Royal Society of London and the other by the American Academy of Arts and Sciences to give awards every two years for outstanding sc of the Royal Society in England. In 1899, at the jubilee commemoration of Sir George Stokes, he was Rede lecturer at Cambridge, his subject being the wave theory of light and its influence on modern physics; and on that occasion the honorary degree of D.Sc. was conferred on him by the university. He died at Paris on April 12, 1902.

The Cornu spiral, a graphical device for the computation of light intensities in Fresnel's model of near-field diffraction, is named after him. The spriral (or clothoid) is also used in geometrical road design.

This article incorporates text from the public domain 1911 Encyclopædia Britannica. 1911 Britannica