Henri Becquerel

Antoine Henri Becquerel (Paris, 15 Desember 1852 – Le Croisic, 25 Agustus 1908) adalah salah seorang fisikawan asal Perancis yang menemukan radioaktivitas. Satuan ukur SI radioaktivitas Becquerel (Bq) dinamakan setelah tokoh ini.

Biography
Early life
Becquerel was born in Paris into a family which, including him and his son Jean, produced four generations of scientists. He studied science at the École Polytechnique and engineering at the École des Ponts et Chaussées. In 1890 he married Louise Désirée Lorieux

Career
In 1892, he became the third in his family to occupy the physics chair at the Muséum National d'Histoire Naturelle. In 1894, he became chief engineer in the Department of Bridges and Highways.
In 1896, while investigating phosphorescence in uranium salts, Becquerel accidentally discovered radioactivity. Investigating the work of Wilhelm Conrad Röntgen, Becquerel wrapped a fluorescent substance, potassium uranyl sulfate, in photographic plates and black material in preparation for an experiment requiring bright sunlight. However, prior to actually performing the experiment, Becquerel found that the photographic plates were fully exposed. This discovery led Becquerel to investigate the spontaneous emission of nuclear radiation.
Describing his method to the French Academy of Sciences on 24 January 1896, he said:
One wraps a Lumière photographic plate with a bromide emulsion in two sheets of very thick black paper, such that the plate does not become clouded upon being exposed to the sun for a day. One places on the sheet of paper, on the outside, a slab of the phosphorescent substance, and one exposes the whole to the sun for several hours. When one then develops the photographic plate, one recognizes that the silhouette of the phosphorescent substance appears in black on the negative. If one places between the phosphorescent substance and the paper a piece of money or a metal screen pierced with a cut-out design, one sees the image of these objects appear on the negative. … One must conclude from these experiments that the phosphorescent substance in question emits rays which pass through the opaque paper and reduces silver salts.[1][2]
In 1903, he shared the Nobel Prize in Physics with Pierre and Marie Curie "in recognition of the extraordinary services he has rendered by his discovery of spontaneous radioactivity"

Honours and awards

Image of Becquerel's photographic plate which has been fogged by exposure to radiation from a uranium salt. The shadow of a metal Maltese Cross placed between the plate and the uranium salt is clearly visible.
In 1908, the year of his death, Becquerel was elected Permanent Secretary of the Académie des Sciences. He died at the age of 55 in Le Croisic.
The SI unit for radioactivity, the becquerel (Bq), is named after him, and there is a Becquerel crater on the Moon and a Becquerel crater on Mars.
• Rumford Medal (1900)
• Helmholtz Medal (1901)
• Nobel Prize for Physics (1903)
• Barnard Medal (1905)

See also
• Antoine César Becquerel (his grandfather)
• A. E. Becquerel (his father)
• Jean Becquerel (his son)

References
1. ^ Henri Becquerel (1896). "Sur les radiations émises par phosphorescence". Comptes Rendus 122: 420–421.
2. ^ Comptes Rendus 122, 420 (1896), translated by Carmen Giunta. Accessed 10 September 2006.

External links
Henri Becquerel - Biography
Becquerel short biography and the use of his name as a unit of measure in the SI
Annotated bibliography for Henri Becquerel from the Alsos Digital Library for Nuclear Issues
Diperoleh dari http://id.wikipedia.org/wiki/Henri_Becquerel