Becquerel, Alexandre Edmond

Antoine-Henri Becquerel, 1852-1908. French physicist and engineer. Discoverer of the rays emitted by uranium. He carried out important researches on rotatory magnetic polarization, phosphorescence, infrared spectra, and radioactivity. His grandfather Antoine-Cesar-Becquerel (1788-1878), and his father, Alexandre-Edmond Becquerel (1820-1891), also made many important contributions to chemistry and physics. 

Antoine-Henri Becquerel was bom the son of the physicist Alexandre-Edmond Becquerel, and the grandson of the physicist Antoine-Cesar Becquerel, and it is not surprising that he followed in their footsteps. It is also not surprising that his research interests centered around solar radiation and phosphorescence, as these are phenomena that his father had investigated. He entered the Ecole Polytechnique, in Paris, in 1872, which he left in 1874 and to which he subsequently returned. Becquerel received a doctorate degree from the Faculty of Sciences of Paris in 1888. In 1892, he was appointed professor of applied physics in the Department of Natural History at the Paris Museum, and in 1895, professor of physics at the Ecole Polytechnique. 

It was Alexandre-Edmond Becquerel, in his 1867 treatise La Lumiere, ses causes et ses ejfets, who first put forward a systematic distinction between fluorescence and phosphorescence. Becquerel designed a phosphoroscope that allowed precise time intervals to elapse between the exposure of a material to light and the observation of the light emitted. He defined fluorescence as emission of light that is immediately extinguished upon removal of the light source, whilst phosphorescence persists for some time after exposure. 

Henri Becquerel (1852-1908) grew up in Paris. His father Alexandre-Edmond Bec-querel was a professor of applied physics and had done research on solar radiation and on luminescence ). Henri studied at the Polytechnic from 1872. In 1892 he was appointed Professor of Applied Physics in the Department of Natural History at the Paris Museum. He became a professor at the Polytechnic in 1895. 

In 1889, still very young, Henri Becquerel was elected a member of the Academie des Sciences de France. His membership there came to be important in coimection with the discovery of uranium radiation. The Becquerel family, Henri s father Alexandre-Edmond and also his grandfather Antoine-Edmond, had been passionately interested in luminescence. Henri himself had, for his father s investigations, prepared beautiful crystals of potassium uranyl sulfate, a substance with fluorescing properties. In his earliest scientific work he also was concerned with the phenomenon of phosphorescence and with the absorption of light by crystals (the subject of his doctoral thesis). 

Becquerel, Antoine Henri (1852-1908) A French physicist who accidendy discovered the existence of radioactivity in 1896. By chance, he put away in a drawer some unexposed photographic plates wrapped in black paper. In the drawer there was also a specimen of uranium salt Later, the plates were found to be fogged and led to the conclusion that the uranium had emitted radiation that was sufflciendy powerful to penetrate the wrapping. In 1903 he was awarded the Nobel Prize for physics with Marie and Pierre Curie. His father (Antoine Cesar) and grandfather (Alexandre Edmond) were also eminent physicists and the three held, one after the other, the position of professor of physics at the Musde d Histoire Naturelle from 1837 to 1908. 

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