Photo from the Nobel Foundation archive.
Antoine Henri Becquerel
Born: 15 December 1852, Paris, France
Died: 25 August 1908, ,
Affiliation at the time of the award: École Polytechnique, Paris, France
Prize motivation: "in recognition of the extraordinary services he has rendered by his discovery of spontaneous radioactivity."
Prize share: 1/2
When Henri Becquerel investigated the newly discovered X-rays in 1896, it led to studies of how uranium salts are affected by light. By accident, he discovered that uranium salts spontaneously emit a penetrating radiation that can be registered on a photographic plate. Further studies made it clear that this radiation was something new and not X-ray radiation: he had discovered a new phenomenon, radioactivity.