Paul Langevin (Langevin Paul)

(1872-1946)
Born January 23, 1872 in Paris. He graduated from the School of Industrial Physics and Chemistry (1891) and Ecole Normale Supц?rieure (1897) in Paris. He worked at the Cavendish Laboratory in Cambridge. In 1900 the laboratory obtained a place in the University of Paris. From 1902 he worked at the College de France (from 1909 - professor), while from 1903 he headed the department in the School of Physics and Chemistry, from 1925 - as director.
Works devoted to the Langevin ionization of gases, quantum theory, relativity theory, ultrasonics, magnetics. In 1905 he developed the theory of dia-and paramagnetism, which gave a clear picture of the phenomenon at the molecular level and allowed to calculate the paramagnetic moment of atoms in a molecule. In 1916 he created the methods for generation of ultra-elastic waves using piezoelectric effect, applied it to the echolocation. In 1925, Langevin has built a powerful emitter of high-frequency acoustic oscillations, constructed underwater ultrasonic transmitter quartz. There are studies Langevin in electrodynamics, electronic, and quantum theory. In 1906 he established independently of the Einstein relation between mass and energy, first came to the concept of mass defect (1913).

Langevin - one of the active members of the League of Human Rights (in the last years of life - its president). He took an active part in the defense of Dreyfus in the work organized in 1933, the Amsterdam Anti-Fascist Committee. A scientific school (L. de Broglie, F.Zholio-Curie, F. Perrin, and others).

Langevin died in Paris on 19 December 1946.