Henri Becquerel

Henri Becquerel was a French physicist who discovered radioactivity in 1896 when he found that uranium salts left near a photographic plate fogged the plate even without exposure to sunlight, showing that the uranium itself was spontaneously emitting some new form of penetrating radiation. His discovery, made while investigating whether phosphorescent materials emitted X-ray-like radiation, opened the field that Marie and Pierre Curie then extended by isolating polonium and radium as far more intensely radioactive elements. Becquerel shared the 1903 Nobel Prize in Physics with the Curies for this work, and the SI unit of radioactivity, the becquerel, is named in his honor.