He continued to present a series of research reports: the second on March 2, the third on March 9, the fourth on March 23, and the fifth on March 30. Henri Becquerel demonstrated that an “unknown radiation” different from phosphorescence is emitted by uranium salts. In the meeting of the Académie des Sciences on March 2, he reported on “Invisible radiation emitted by a phosphorescent substance”. From this, he came to the conclusion that the experimental sample emitted a type of radiation similar to X-rays. 2) of the phosphorescent substance, clearer than that in the earlier experiment, was seen even with little exposure to sunlight. Then, contrary to his expectation, an image (Fig. However, he hurried to develop the plates for the meeting of the Académie des Sciences. That year was a leap year and February 29 and March 1 were also cloudy days. The experimental sample had been left in the dark in the drawer of a table. However, on February 26 and 27, 1896, the weather in Paris was cloudy, and the experiment was stopped in the middle. He had planned to develop the plates after exposing the samples to sunlight. Then he prepared several crystalline samples with their one side covered by an aluminum plate. To confirm that K(UO)SO 4 + H 2O is highly phosphorescent, Henri Becquerel wrapped a new photosensitive plate in an opaque black cloth. In a regular meeting of the Académie des Sciences on February 24, 1896, he presented a lecture on “Radiation produced by phosphorescence”. When the plate was subsequently developed, a shadow of the phosphorescent substance was seen. Then, he exposed the whole package to sunlight for several hours. Because Henri Becquerel knew from his father’s work that uranium compounds generate phosphorescence, he thought that X-ray-like radiation might be emitted by strongly phosphorescent substances.Īs a phosphorescent substance, Henri Becquerel used a thin section of a uranium–potassium double sulfate crystal K(UO)SO 4 + H 2O, which was placed over a photosensitive plate made from gelatin and silver bromide wrapped in two layers of thick black paper without exposing it to sunlight. Henri Becquerel, who was present as one of the members, asked, “From which side of the discharge tube are the X-rays coming?” Poincare replied, “They seem to have been emitted from where the glass on the side opposite the negative electrode emits phosphorescence”. Röentgen among the members of the Académie des Sciences for their inspection. In a regular meeting of the Académie des Sciences on January 20, 1896, the famous mathematician and astronomer Jules Henri Poincaré, professor at the University of Paris, circulated an X-ray photograph received directly from W. He became a leading scientist in the field of phosphorescence and fluorescence along with his father, and he held high-ranking positions in academic societies with his many research achievements. He was also selected as a member of the Académie des Sciences, published research articles on fluorescence and phosphorescence, and joined the École Polytechnique as a professor. He received a degree of Doctor of Science from the University of Paris.
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Footnote 3 For some time, he worked in the Ministry of Construction as a civil engineer, but after pursuing research as an assistant to his father, he also became a professor of applied physics at the Musée d’ Histoire Naturelle in 1892. In 1874, he was enrolled at the École des Ponts et Chaussées and studied civil engineering for 3 years. He designed a phosphoroscope with which he measured the intensity and duration of the fluorescence of uranium under various lightrays.Īntoine Henri Becquerel of the third generation entered the École Polytechnique in 1872.
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Moreover, he was an authority on fluorescence and had a particularly good knowledge about uranium. He conducted scientific research on the effect of light, and he was among those who photographed the spectrum of sunlight for the first time.
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He was also a professor at the Musée d’ Histoire Naturelle. His father, Alexandre Edmond Becquerel (1820–1891), started as an assistant and became a professor at the École Polytechnique.
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After that, he became a first-generation professor in the department of applied physics of the Musée d’ Histoire Naturelle, Footnote 2 which is dedicated to scientific research. Footnote 1 He joined the army during the war waged by Napoleon against Spain. His grandfather, Antoine César Becquerel (1788–1878), was a member of the inaugural class of the École Polytechnique.