Antoine Henri Becquerel (15.XII.1852-25.08.1908) was a French physicist and a member of the Paris Academy of Sciences (1889), its president in 1908. He was the son of A. E. Becquerel. He was born in Paris. He graduated from the École Polytechnique in Paris (1874); from 1876 he was a lecturer at that school and from 1895 a professor (from 1892 he was also head of the chair of physics at the Museum of Natural History and at the Conservatoire des Arts et Métiers).
His main work concerned optics (magneto-optics, phosphorescence, infrared spectra) and radioactivity. In 1896, while studying the action of various luminescent substances on a photographic plate, uranium salts among them, he discovered an unknown radiation belonging to the uranium salt itself and having nothing in common with luminescent emission. This phenomenon of the spontaneous emission by uranium salts of rays of a particular nature was named radioactivity. For the discovery of the phenomenon of the natural radioactivity of uranium Becquerel was awarded the Nobel Prize in 1903. By passing beta rays through crossed electric and magnetic fields, he was the first to measure the ratio of charge to mass of beta particles and established that it is of the same order as for the particles of cathode rays (1900). In 1901 he detected (independently of P. Curie) the physiological action of radioactive radiation, and also its ability to ionise a gas.
A member of a number of academies of sciences