Henri Becquerel

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Antoine Henri Becquerel

Henri Becquerel.jpg
Antoine Becquerel, French physicist
Born

December 15, 1852
Paris, France

Died August 25, 1908

Le Croisic, Brittany, France

Residence Flag of France (bordered).svg France
Nationality Flag of France (bordered).svg French
Field Physicist
Institutions Conservatoire des Arts et Metiers
École Polytechnique
Paris Museum
Alma mater École Polytechnique
École des Ponts et Chaussées
Known for Radioactivity
Notable prizes Nobel.svg Nobel Prize for Physics (1903)
Note that he is the father of Jean Becquerel, the son of A. E. Becquerel, and the grandson of

Antoine César Becquerel.

Image of Becquerel's photographic plate that was fogged by exposure to radiation from uranium salts. The shadow of a metal Maltese Cross placed between the plate and the uranium salts is clearly visible.

Antoine Henri Becquerel (December 15, 1852 – August 25, 1908) was a French physicist, Nobel laureate, and one of the discoverers of radioactivity.

Early days and family

Henri Becquerel was born in Paris, France to a family which, including himself and his son, produced four generations of scientists. Henri's grandfather, Antoine Cesar Becquerel, invented a method of extracting metals from ores using electrolysis. His father, Alexander Edmond Becquerel, was a physicist who researched solar phenomena and phosphorescence.

As child, young Henri loved to visit his father's laboratory and took great delight in examining the various experimental set ups he found there. Written accounts of that period of his life suggest there was a close relationship between father and son in the passing on of the scientific tradition. Two preceding generations of scientists gave Henri Becquerel the impetus to further illuminate the truth through scientific research.

Education, Engineering and Theoretical physics

Antoine Henri Becquerel was educated at Lycee Louis-le-Grand during his early years. He moved on to the Ecole Poytechnique and finally the Ecole des Ponts et Chaussees. His direction in life seems to have been always focussed on science. He won his engineering degree in 1877 and served with the National Administration of Bridges and Highways while maintaining an interest in problems of a scientific and theoretical nature. He later accepted a teaching position in physics at the Conservatoire des Arts et Metiers in 1878. Within ten years he had earned his doctorate with a dissertation on the absorption of light by crystals.

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 discovered radioactivity accidentally. Investigating the work of Wilhelm Conrad Röntgen, Becquerel wrapped a fluorescent mineral, 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 January 24, 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]

Research and Discovery

Early in his career as a research physicist, Henri Becquerel developed laws of radiation of light from phosphorescent substances. While attending a lecture on the discovery of "X-rays", Becquerel's attention was captured by the mention of a flouroscope, a device which his father had invented. Shortly afterward he began his own study of X-rays, reproducing Roentgen's experiments. He became intirgued by a suspicion that fluorescent materials just might contain some of these mysterious "X-rays".

In 1896 he began working with crystals of a compound containing uranium, which having been exposed to sunlight, later emitted fluorescent light. He intended to prove that radiation was present by preparing a photographic plate and exposing a sample of the uranium salt to the sun. By chance a cloudy period ensued during which no sunlight was available. Becquerel at an impasse. He next wrapped the crystals and a copper cross in a black cloth with the photosensitive plate and put them in a drawer intending to retrieve them later. Quite a number of rainy days followed with no sunlight. Becquerel finally removed the plate from the drawer and developed it expecting he might see some faint evidence of emission. To his immense surprise the photo plate revealed a distinct image of the copper cross, evidence of strong radiation which must have come from the uranium compound itself. He began to research these energetic emissions which were then called "Becquerel rays." Becquerel published a half dozen papers exploring this phenomenon and then turned his attention to other interests.

Later, upon learning of studies on radiation being conducted by the husband and wife team of Pierre and Marie Curie, Becquerel became interested. He assisted the team in obtaining two Academy of Science grants for Marie Curie's work. With Becquerel's support, the Curies published their findings on radium in the journal of the Academy of Science in France. Marie Curie was the first to coin the word "radiation" to describe the rays of Becquerel and those which she and Pierre discovered emanating from radium.

Becquerel meanwhile conducted his own research on the phenomena of radiation and in 1899 declared that the rays could be deflected by a magnetic field which suggested they were at least partially particles. In 1900, he was clearly committed to the idea that the radiations had to include particles of negative charge—just like the cathode rays discovered by J.J. Thompson.

Although Becquerel was the only one of the three present at the awarding of the Nobel Prize for Physics in 1903, it was clear that he and the Curie s each deserved recognition for their unique contributions to the understanding a newly discovered phenomenon called "radioactivity".

  • Spouse: Louise Désirée Lorieux (m. 1890)
  • Children: Jean

Later education and return to theoretical physics

Antoine Henri Becquerel was educated at Lycee Louis-le-Grand during his early years. He moved on to the Ecole Poytechnique and finally the Ecole des Ponts et Chaussees. His direction in life seems to have been always focussed on science. He won his engineering degree in 1877 and served with the National Administration of Bridges and Highways while maintaining an interest in problems of a scientific and theoretical nature. He later accepted a teaching position in physics at the Conservatoire des Arts et Metiers in 1878. Within ten years he had earned his doctorate with a dissertation on the absorption of light by crystals.

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 discovered radioactivity accidentally. Investigating the work of Wilhelm Conrad Röntgen, Becquerel wrapped a fluorescent mineral, 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 January 24, 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."

In 1908, Becquerel was elected permanent secretary of the Académie des Sciences. He died the same year, at the age of 55, in Le Croisic.

Honors

  • Rumford Medal (1900)
  • Helmholtz Medal (1901)
  • Nobel Prize for Physics (1903)
  • Barnard Medal (1905)

Named after him

  • The SI unit for radioactivity, the becquerel (Bq), is named after him.
  • A crater on the Moon and another on Mars have been named Becquerel craters.

Legacy

Becquerel possessed the ability to formalize experimental results into precise mathematical statements. His surprise discovery of the emission of rays of energy from a salt of uranium contributed to a change in the paradigm of classical physics and thus a more detailed understanding of the nature of matter and its relationship to energy. Henri Becquerel’s exploration of invisible but detectible emanations coming from within the atom itself led to a pivotal redefinition of the nature and structure of the atom and consequently helped introduce a revolutionary era of atomic physics and led to new thought about the relationship between matter and energy. 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."

(Include or not as seems appropriate) Marie Curie’s search for a research topic to support her Phd in Physics led her to the published papers of Becquerel on “uranic rays” also called “Becquerel Rays.” The outcome was a collaboration between teacher and student that made Nobel prize history. Henri Becquerel can be seen as a pioneer in a new world of subatomic phenomena at the close of the 19th century. and in collaboration or competition with others such as the Curies and Roentgen he began to open the door to the modern atomic age.


See also

Notes

  1. Becquerel, Henri. 1896. Sur les radiations émises par phosphorescence. Comptes Rendus 122:420-421. Retrieved November 7, 2007.
  2. Antoine Henri Becquerel (1852-1908) Presentations before the French Academy of Science in 1896, translated by Carmen Giunta. Retrieved November 7, 2007.

References
ISBN links support NWE through referral fees

  • Asimov, Isaac. 1982. Asimov's Biographical Encyclopedia of Science and Technology. 2nd ed. Garden City, NY: Doubleday. ISBN 0385177712.
  • Goldsmith, Barbara. 2005. Obsessive Genius: The Inner World of Marie Curie. Great Discoveries. New York: W.W. Norton & Co. ISBN 0393327485.
  • Tiner, John Hudson. 2000. 100 Scientists Who Shaped World History. 100 series. San Mateo, California: Bluewood Books. ISBN 0912517395.
  • Sootin, Harry. 1960. 12 Pioneers of Science. New York, NY: Vanguard Press. ASIN B0007EP3UG.
  • Jones, Bessie Zaban, ed. 1966. The Golden Age of Science: Thirty Portraits of the Giants of 19th - Century Science by Their Scientific Contemporaries. New York: Simon and Schuster, in cooperation with the Smithsonian Institution, Washington.

External links

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