Henri Becquerel

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Henri Becquerel. (credit: Archives Photographiques)

(born Dec. 15, 1852, Paris, France — died Aug. 25, 1908, Le Croisic) French physicist. His grandfather, Antoine-César (1788 – 1878), was one of the founders of the field of electrochemistry, and his father, Alexandre-Edmond (1820 – 91), made important studies of light phenomena. Henri likewise studied phosphorescent materials as well as uranium compounds and employed photography in his experiments. He is remembered for his discovery of radioactivity, which occurred when he found that the element uranium (in a sample of pitchblende) emitted invisible rays that could darken a photographic plate. His 1901 report of a burn caused by a sample of Marie Curie's radium that he carried in his vest pocket led to investigations by physicians and ultimately the medical use of radioactive substances. In 1903 he shared a Nobel Prize for Physics with the Curies. The unit of radioactivity, the becquerel (Bq), is named for him.

For more information on Antoine- Henri Becquerel, visit Britannica.com.

French physicist (1852–1908)

Becquerel was born in Paris; his early scientific and engineering training was at the Ecole Polytechnique and the School of Bridges and Highways, and in 1876 he started teaching at the Polytechnique. From 1875 he researched into various aspects of optics and obtained his doctorate in 1888. In 1899 he was elected to the French Academy of Sciences, continuing the family tradition as his father and grandfather, both renowned physicists, had also been members. He held chairs at the Ecole Polytechnique, the Museum of Natural History, and the National Conservatory of Arts and Crafts, and became chief engineer in the department of bridges and highways.

Becquerel is remembered as the discoverer of radioactivity in 1896. Following Wilhelm Röntgen's discovery of x-rays the previous year, Becquerel began to look for x-rays in the fluorescence observed when certain salts absorb ultraviolet radiation. His method was to take crystals of potassium uranyl sulfate and place them in sunlight next to a piece of photographic film wrapped in black paper. The reasoning was that the sunlight induced fluorescence in the crystals and any x-rays present would penetrate the black paper and darken the film.

The experiments appeared to work and his first conclusion was that x-rays were present in the fluorescence. The true explanation of the darkened plate was discovered by chance. He left a plate in black paper next to some crystals in a drawer and some time later developed the plate. He found that this too was fogged, even though the crystals were not fluorescing. Becquerel investigated further and discovered that the salt gave off a penetrating radiation independently, without ultraviolet radiation. He deduced that the radiation came from the uranium in the salt.

Becquerel went on to study the properties of this radiation; in 1899 he showed that part of it could be deflected by a magnetic field and thus consisted of charged particles. In 1903 he shared the Nobel Prize for physics with Pierre and Marie Curie.

The French physicist Antoine Henri Becquerel (1852-1908) was the discoverer of natural radioactivity.

Antoine Henri Becquerel was born in Paris on Dec. 15, 1852. Both his father, Alexandre Edmond Becquerel, and his grandfather, Antoine César Becquerel, were scientists. Following his graduation from the École Polytechnique in 1874, Antoine Henri worked as a civil engineer, but he also retained a strong interest in scientific problems. In 1878 he succeeded in the chair of his father who was professor of applied physics at the Conservatoire des Arts et Métiers. Ten years later Becquerel earned his doctor's degree with a dissertation on the absorption of light in crystals. He then became professor of applied physics at the Museum of Natural History in Paris in 1892 and professor of physics at the Polytechnique in 1895.

Prior to 1895 Becquerel did research on phosphorescence. He had inherited from his father a supply of uranium salts, which were known to be phosphorescent when exposed to light. Upon learning in January 1896 about W. C. Roentgen's discovery of x-rays, Becquerel's interest immediately turned to the question of whether all phosphorescent materials acted as sources of similar rays.

The results did not justify his hopes, but Becquerel stumbled on an unexpected phenomenon. After placing sheets of sulfate of uranium on photographic plates wrapped in black paper, he exposed the package to light for several hours. On developing the plates he obtained distinct pictures of the uranium sheets. Later he obtained pictures of medals which had been placed between the uranium and the plates. The uneven thickness of the medals blocked in varying degrees the effectiveness of the radiation from uranium. He also discovered that part of the radiation could be deflected by a magnetic field and that the radiations had an ionizing effect on the surrounding air.

For the discovery of natural radioactivity, which for a number of years was called Becquerel rays, he won the Nobel Prize in physics in 1903. In his Nobel lecture Becquerel noted that the new radiation indicated the possible modification of atoms which "the methods at our disposal are unable to bring about (but which) could certainly release energy in sufficiently large quantities to produce the observed effects, without the changes in matter being large enough to be detectable by our methods of investigation." As a cause of that modification, he held out the possible existence of "an external radiation" hitherto undetected but which, when absorbed by radioactive materials, would be transformed into radioactivity without bringing about the transformation of the atoms themselves.

Becquerel's election as perpetual secretary of the Academy of Sciences in 1908 was one of the numerous honors bestowed on him. His death on Aug. 25, 1908, at Le Croisic did not signal the end of the lineage of scientists in the Becquerel family. From Becquerel's marriage to Lucie Zoé Marie Jamin a son, Jean, had been born; he became the fourth Becquerel to occupy the chair of physics at the Museum of Natural History and was also an able investigator of radioactivity.

Further Reading

The major work on Becquerel is in French. A detailed account of Becquerel's life is in Bessie Zaban Jones, ed., The Golden Age of Science: Thirty Portraits of the Giants of 19th-century Science by their Scientific Contemporaries (1966). Nobel Lectures: Physics, 1901-1921 (1964), published by the Nobel Foundation, includes a biographical sketch of Becquerel as well as his Nobel lecture on radioactivity. A biographical sketch is also contained in Niels Hugh de Vaudrey Heathcote, Nobel Prize Winners in Physics, 1901-1950 (1953). For background material see Harvey E. White, Classical and Modern Physics (1940).

Quotes:

"Decisiveness is often the art of timely cruelty."

For other uses, see Becquerel (disambiguation).

Antoine Henri Becquerel
Henri Becquerel, French physicist
Born	15 December 1852(1852-12-15) Paris, France
Died	25 August 1908 (aged 55) Le Croisic, Brittany, France
Nationality	France
Fields	Physics, chemistry
Institutions	Conservatoire des Arts et Metiers École Polytechnique Muséum National d'Histoire Naturelle
Alma mater	École Polytechnique École des Ponts et Chaussées
Doctoral students	Marie Curie
Known for	Radioactivity
Notable awards	Nobel Prize in Physics (1903)
Religious stance	Roman Catholic
Notes Note that he is the father of Jean Becquerel, the son of A. E. Becquerel, and the grandson of Antoine César Becquerel.

Antoine Henri Becquerel (15 December 1852 – 25 August 1908) was a French physicist, Nobel laureate, and the discoverer of radioactivity, for which he won the 1903 Nobel Prize in Physics (along with Marie Curie and Pierre Curie who had found additional radioactive elements).

Contents 1 Biography 1.1 Early life 1.2 Career 2 Honours and awards 3 See also 4 References 5 External links

Biography

Early life

Becquerel was born in Paris into a family which produced four generations of scientists, including Becquerel's own son Jean. 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 already exposed, showing the image of the substance. 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. There is a crater called Becquerel on the Moon and also a crater called Becquerel on Mars.

He also received the following awards besides the Nobel Prize for Physics (1903):

• Rumford Medal (1900)
• Helmholtz Medal (1901)
• 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. http://gallica.bnf.fr/ark:/12148/bpt6k30780/f422.chemindefer. 
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

v • d • e Nobel Laureates in Physics Wilhelm Röntgen (1901) · Hendrik Lorentz / Pieter Zeeman (1902) · Henri Becquerel / Pierre Curie / Marie Curie (1903) · Lord Rayleigh (1904) · Philipp Lenard (1905) · J. J. Thomson (1906) · Albert Michelson (1907) · Gabriel Lippmann (1908) · Guglielmo Marconi / Ferdinand Braun (1909) · Johannes van der Waals (1910) · Wilhelm Wien (1911) · Gustaf Dalén (1912) · Kamerlingh Onnes (1913) · Max von Laue (1914) · W. L. Bragg / W. H. Bragg (1915) · Charles Barkla (1917) · Max Planck (1918) · Johannes Stark (1919) · Charles Guillaume (1920) · Albert Einstein (1921) · Niels Bohr (1922) · Robert Millikan (1923) · Manne Siegbahn (1924) · James Franck / Gustav Hertz (1925) Complete roster | (1901–1925) | (1926–1950) | (1951–1975) | (1976–2000) | (2001–present)

Persondata
NAME	Becquerel, Antoine Henri
ALTERNATIVE NAMES
SHORT DESCRIPTION	French physicist
DATE OF BIRTH	15 December 1852
PLACE OF BIRTH	Paris, France
DATE OF DEATH	25 August 1908
PLACE OF DEATH	Le Croisic, Brittany, France

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