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Famous Scientists Henri Becquerel French physicist Henri Becquerel (1852–1908) was the discoverer of radioactivity, for which he won the 1903 Nobel Prize in Physics (sharing it with Marie and Pierre Curie). He had been researching X-rays—a phenomenon discovered in 1895 by the German physicist Wilhelm Röntgen (1845–1923). X-rays are like light, but have much shorter wavelengths and can pass through some solids. Becquerel wanted to investigate whether there was any connection between X-rays and naturally occurring phosphorescence. He found that the chemical compounds containing the element uranium also gave out rays, but which were different from X-rays—they could be deflected by electric or magnetic fields. These new rays left a foggy mark on a light-sensitive photographic plate. Becquerel could not explain why this had occurred, even when it was wrapped in paper. Marie Curie worked out how to measure this radiation, naming it "radioactivity".