Antoine Henri Becquerel Physicist Date of Birth: 15.12.1852 Country: France

Biography of Antoine Henri Becquerel

Antoine Henri Becquerel, a French physicist, was born in Paris. He came from a family of renowned scientists, with his father, Alexandre Edmond, and his grandfather, Antoine César, both being professors of physics at the Museum of Natural History in Paris and members of the French Academy of Sciences.

Becquerel received his secondary education at the Lycée Louis-le-Grand and in 1872, he entered the Polytechnic School in Paris. After two years, he transferred to the Higher School of Bridges and Roads, where he studied engineering, taught, and conducted independent research. In 1875, he began studying the effect of magnetism on linearly polarized light, and the following year, he started his teaching career as a lecturer at the Polytechnic School. He obtained his scientific degree in engineering from the Higher School of Bridges and Roads in 1877 and began working at the National Administration of Bridges and Roads. A year later, Becquerel became his father's assistant at the Museum of Natural History, while continuing to work at the Polytechnic School and the Administration of Bridges and Roads. He collaborated with his father for four years, writing a series of articles on the temperature of the Earth.

After completing his own research on linearly polarized light in 1882, Becquerel continued his father's investigations into luminescence, the non-thermal emission of light. In the mid-1880s, he also developed a new method for analyzing spectra, the combinations of waves of different lengths emitted by a light source. In 1888, he obtained his doctorate from the Faculty of Natural Sciences at the University of Paris for his dissertation on the absorption of light in crystals. In 1892, a year after his father's death, Becquerel succeeded him as the head of the physics department at the Conservatory of Arts and Crafts, as well as a similar department at the Museum of Natural History in Paris. Two years later, he became the chief engineer at the Administration of Bridges and Roads, and in 1895, he obtained a chair in physics at the Polytechnic School.

In 1895, German physicist Wilhelm Röntgen discovered a highly energetic and penetrating form of radiation, now known as X-rays, which are produced when cathode rays (electrons) emitted by the negative electrode (cathode) of an electron vacuum tube strike another part of the tube during a high-voltage discharge. Since the cathode rays also caused luminescence when they struck the tube, it was mistakenly believed that both luminescence and X-rays were produced by the same mechanism and that luminescence could be accompanied by X-rays. Intrigued by this, Becquerel set out to determine if a luminescent material, activated by light instead of cathode rays, could also emit X-rays. He placed luminescent material, potassium uranyl sulfate (one of the salts of uranium) that he had on hand, on photographic plates wrapped in dense black paper and exposed the package to sunlight for several hours. Afterwards, he discovered that the radiation passed through the paper and affected the photographic plate, indicating that the uranium salt emitted X-rays as well as light after being exposed to sunlight. However, to Becquerel's surprise, the same effect occurred when the package was placed in a dark place, without being exposed to sunlight. It seemed that Becquerel was observing the result of the action of not X-rays, but a new type of penetrating radiation emitted spontaneously without the external exposure of a source. Over the next few months, Becquerel repeated his experiment with other known luminescent substances and found that only uranium compounds emitted the spontaneous radiation he had observed. Furthermore, non-luminescent uranium compounds also emitted similar radiation, indicating that it was not related to luminescence. In May 1896, Becquerel conducted experiments with pure uranium and found that the photographic plates showed a degree of exposure that was three to four times greater than the exposure from the initially used uranium salt. This mysterious radiation, which clearly had a property inherent to uranium, became known as Becquerel rays.

Over the next few years, through the research of Becquerel and other scientists, it was discovered, among other things, that the power of radiation did not seem to decrease over time. By 1900, Becquerel concluded that these rays partially consisted of electrons, which had been discovered in 1897 by J.J. Thomson as components of cathode rays. Becquerel's student, Marie Curie, discovered that thorium also emitted Becquerel rays and renamed them as radioactivity. She and her husband, Pierre Curie, after thorough research, discovered two new radioactive elements - polonium and radium. Becquerel and the Curie couple were awarded the Nobel Prize in Physics in 1903. Becquerel was particularly honored "in recognition of his outstanding merits expressed in the discovery of spontaneous radioactivity." In his welcome speech on behalf of the Royal Swedish Academy of Sciences, X.R. Thunberg stated that the laureates had demonstrated "those special types of radiation, which until now were known only from electrical discharges in rarefied gases, are natural and widespread phenomena." Thunberg added that "new methods have been obtained, enabling the existence of matter in nature to be studied under certain conditions. Finally, a new source of energy has been found, the complete interpretation of which is still ahead."

Becquerel married Lucie Zoé Marie Jamin, the daughter of a physics professor, in 1874. Four years later, his wife died during childbirth, giving birth to their only child, Jean, who later became a physicist. In 1890, Becquerel married Louise Désirée Lorée. After receiving the Nobel Prize, he continued his teaching and scientific work. Becquerel passed away in 1908 in Le Croisic, Brittany, during a trip with his wife to her ancestral estate. In addition to the Nobel Prize, Becquerel received numerous honors, including the Rumford Medal from the Royal Society of London (1900), the Helmholtz Medal from the Berlin Academy of Sciences (1901), and the Barnard Medal from the American National Academy of Sciences (1905). He was elected a member of the French Academy of Sciences in 1899 and became one of its permanent secretaries in 1908. Becquerel was also a member of the French Physical Society, the Italian National Academy of Sciences, the Berlin Academy of Sciences, the American National Academy of Sciences, and the Royal Society of London.