Jean Baptiste Perrin (30.09.1870-17.04.1942) — French physicist and physical chemist, a member of the Paris Academy of Sciences (1923) and its president in 1936. He was born in Lille. He graduated from the École Normale (1894), where in 1897 he received his doctorate. From 1898 he was at the University of Paris (professor from 1910). From 1938 he lived in the USA.
In 1895 he proved experimentally that cathode rays are a stream of negatively charged particles. In 1908 he carried out a series of experimental studies of Brownian motion which confirmed the molecular-statistical theory of Einstein — Smoluchowski and finally convinced physicists that Brownian motion is a consequence of the thermal motion of the molecules of the medium, and that the molecules themselves are real. From his experiments he calculated (1909) the Avogadro number, 6.8*1023. Studying the structure of soap films in 1918—19, he showed that the smallest thickness of a film is equal to two molecular layers and that any film consists of a whole number of bimolecular layers. His work also concerned X-rays, the conductivity of gases, fluorescence, radioactivity, atomic physics and acoustics. He developed (1901) the planetary model of the atom (the Perrin model).
He fought against fascism and was an active friend of the USSR. Nobel Prize (1926). A foreign member of the USSR Academy of Sciences (1929).
In 1895 he proved experimentally that cathode rays are a stream of negatively charged particles. In 1908 he carried out a series of experimental studies of Brownian motion which confirmed the molecular-statistical theory of Einstein — Smoluchowski and finally convinced physicists that Brownian motion is a consequence of the thermal motion of the molecules of the medium, and that the molecules themselves are real. From his experiments he calculated (1909) the Avogadro number, 6.8*1023. Studying the structure of soap films in 1918—19, he showed that the smallest thickness of a film is equal to two molecular layers and that any film consists of a whole number of bimolecular layers. His work also concerned X-rays, the conductivity of gases, fluorescence, radioactivity, atomic physics and acoustics. He developed (1901) the planetary model of the atom (the Perrin model).
He fought against fascism and was an active friend of the USSR. Nobel Prize (1926). A foreign member of the USSR Academy of Sciences (1929).