Henri Becquerel was a French physicist who discovered radioactivity through his investigations of uranium and other substances.
Becquerel had become a highly respected physicist by 1896. After the discovery of the x-ray in 1895, Becquerel began to investigate whether there was a fundamental connection between this form of invisible radiation and visible light.
His expertise with phosphorescent materials, his familiarity with uranium compounds, and his general skill in laboratory techniques, including photography, all played a key role in his discovery of radioactivity. Becquerel experimented by placing phosphorescent crystals on a sealed photographic plate that had been wrapped in opaque paper, and never exposed to direct light.
After the plate was developed, images were visible on it. He passed the results on to Madame Curie, who named this phenomenon radioactivity. In 11903, Becquerel shared the Nobel Prize for physics with the chemists Pierre and Marie Curie.