Portrait of the French physicist Antoine Henri Becquerel (1852-1908). He was mainly educated at the Ecole Polytechnique in Paris where he became professor of physics in 1895. In 1896 Becquerel discovered the phenomenon of radioactivity showing that a uranium salt was able to blacken a wrapped photographic plate. In 1899 he noted that the radiation coming from the uranium salt could be deflected by a magnetic field. This allowed Becquerel to conclude that this radiation was partly composed of electrons discovered a few years before by J. J. Thomson. In 1903 Becquerel shared the Nobel Prize in physics with the Curies.