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Particle Decays And Annihilations : Radioactivity In the late 1800s the German physicist Wilhelm Röntgen discovered a strange new ray produced when an electron beam struck a piece of metal. Since these were rays of an unknown nature, he called them "x rays".
![]() ![]() ![]() ![]() ![]() ![]() Two months after this discovery, the French physicist Henri Becquerel was studying fluorescence when he found that photographic plates were exposed in the presences of some elements, even when the plates were wrapped in black paper. Becquerel realized that these elements, including uranium, emitted energetic rays without any energy input.
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