Edmond Becquerel

Not to be confused with his son, Nobel laureate Henri Becquerel.

Edmond Becquerel
Born	(1820-03-24)24 March 1820 Paris
Died	11 May 1891(1891-05-11) (aged 71)
Known for	First observed the photovoltaic effect Overhead projector Phosphoroscope Thermionic emission
Children	Henri Becquerel
Parent	Antoine César Becquerel
Scientific career
Fields	Physics

Alexandre-Edmond Becquerel (French pronunciation: [alɛksɑ̃dʁ ɛdmɔ̃ bɛkʁɛl]; 24 March 1820 – 11 May 1891), known as Edmond Becquerel, was a French physicist who studied the solar spectrum, magnetism, electricity and optics. He is credited with the discovery of the photovoltaic effect, the operating principle of the solar cell, in 1839. He is also known for his work in luminescence and phosphorescence. He was the son of Antoine César Becquerel and the father of Henri Becquerel, one of the discoverers of radioactivity.

Biography

Becquerel was born in Paris and was in turn the pupil, assistant and successor of his father at the Muséum national d'Histoire naturelle. He was also appointed professor at the short-lived Agronomic Institute at Versailles in 1849, and in 1853 received the chair of physics at the Conservatoire des Arts et Métiers. He was associated with his father in much of his work.

The first photovoltaic device

In 1839, at age 19, experimenting in his father's laboratory, Becquerel created the world's first photovoltaic cell. In this experiment, silver chloride or silver bromide was used to coat the platinum electrodes; once the electrodes were illuminated, voltage and current were generated. Because of this work, the photovoltaic effect has also been known as the "Becquerel effect".

Photographic discoveries

Becquerel was an early experimenter in photography. In 1840, he discovered that the silver halides, natively insensitive to red and yellow light, became sensitive to that part of the spectrum in proportion to their exposure to blue, violet and ultraviolet light, allowing daguerreotypes and other photographic materials to be developed by bathing in strong red or yellow light rather than by chemical treatment. In practice this technique was rarely used. In 1848 he produced color photographs of the solar spectrum, and also of camera images, by a technique later found to be akin to the Lippmann interference method, but the camera exposures required were impractically long and the images could not be stabilized, their colors persisting only if kept in total darkness, however this work is based on the discoveries of J. T. Seebeck prior to 1810.

Other studies

Becquerel paid special attention to the study of light, investigating the photochemical effects and spectroscopic characters of solar radiation and the electric arc light, and the phenomena of phosphorescence, particularly as displayed by the sulfides and by compounds of uranium. It was in connection with these latter inquiries that he devised his phosphoroscope, an apparatus which enabled the interval between exposure to the source of light and observation of the resulting effects to be varied at will and accurately measured.

He investigated the diamagnetic and paramagnetic properties of substances and was keenly interested in the phenomena of electrochemical decomposition, accumulating much evidence in favor of Faraday's law of electrolysis and proposing a modified statement of it which was intended to cover certain apparent exceptions. In 1853, Becquerel discovered thermionic emission.

Publications

In 1867 and 1868 Becquerel published La lumière, ses causes et ses effets (Light, its Causes and Effects), a two-volume treatise which became a standard text. His many papers and commentaries appeared in French scientific journals, mainly the French Academy of Science's widely distributed Comptes Rendus, from 1839 until shortly before his death in 1891.

Honors and awards

Becquerel was elected a member of the Royal Swedish Academy of Sciences in 1886.

The Becquerel Prize for "outstanding merit in photovoltaics" is awarded annually at the European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC).

See also

• Phosphoroscope

Further reading

• A. Allisy (1 November 1996). "Henri Becquerel: The Discovery of Radioactivity". Radiation Protection Dosimetry. 68 (1): 3–10. doi:10.1093/oxfordjournals.rpd.a031848.
• Chisholm, Hugh, ed. (1911). "Becquerel" . Encyclopædia Britannica. Vol. 3 (11th ed.). Cambridge University Press. p. 611.

External links

• Works by or about Edmond Becquerel at the Internet Archive
• Works in Open Library