Henri becquerel

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Antoine Henri Becquerel (Paris, December 15, 1852-Le Croisic, August 25, 1908) was a French physicist who discovered radioactivity and was awarded the Nobel Prize in Physics for year 1903, shared with Pierre Curie and Marie Curie.

He was born into a wealthy family that produced four generations of scientists: his grandfather Antoine César Becquerel, his father Alexandre Edmond Becquerel, and his son Jean Becquerel.

Biography

Son of Alexandre-Edmond Becquerel, who studied light and phosphorescence and invented phosphoroscopy, and also grandson of Antoine César Becquerel, one of the founders of electrochemistry.

Becquerel was born in Paris, into a wealthy family that produced four generations of physicists: his grandfather, his father, and his son.

After completing primary education at the Lycée Louis-le-Grand, he studied and received his doctorate in science at the École Polytechnique and the École des Ponts et Chaussées in Paris. In 1874 he married Lucia Jamin (daughter of Jules Jamin, one of his physics professors at the Polytechnic). The couple had a son, Jean (1878-1953). Lucia Zoé Marie Jamin, died while giving birth to her son, Jean. After being widowed, in 1890 he married Louise Lorieux (1864-1945) for the second time, daughter of Edmond Lorieux, Inspector General of Mines, and niece of Théodore-Marie Lorieux, vice-president of the General Council for Bridges and Roads.

He was a professor at the Natural History Museum in 1892 and at the École Polytechnique in 1895.

He graduated as an engineer in 1877 and devoted himself to research. His first works focused on optics, but from 1875 he began his research on electromagnetic polarization. In 1883, he studied the infrared spectrum of metallic vapors, before devoting himself, in 1886, to the absorption of light by crystals. He defended his doctoral thesis in 1888 (Recherches sur l'absorption de la lumière, research on the absorption of light).

In Becquerel's early career, he became the third in his family to hold the chair of physics at the National Museum of Natural History in 1892. Later in 1894, Becquerel became chief engineer in the Department of Bridges and Caminos before he began his first experiments. Becquerel's early works focused on the subject of his doctoral thesis: the polarization of light, with the phenomenon of phosphorescence and absorption of light by crystals.Early in his career, Becquerel also studied the magnetic fields of the earth.

In 1889 he was elected to the French Academy of Sciences, an institution to which his father and grandfather had belonged. After his father's death in 1892, he continued his work and eventually became professor at the École Polytechnique in 1895, where he succeeded Alfred Potier.

Becquerel did not survive much longer after his discovery of radioactivity and died on August 25, 1908, at the age of 55, in Le Croisic, France. His death was of unknown causes, but it was reported that " he had developed severe skin burns, probably from handling radioactive materials."

Scientific research

In 1896 he discovered a new property of matter that was later called natural radioactivity. This phenomenon occurred during his research on fluorescence. By placing uranium salts on a photographic plate in a dark area, he found that the plate blackened. The uranium salts emitted radiation capable of passing through black paper and other substances opaque to ordinary light. These rays were originally called Becquerel rays in honor of the discoverer of him. His research and discoveries served as the basis for the first atomic models.

In 1900 he found that beta radiation is made up of electrons and in 1901 that radium could be used to destroy tumors, the origin of radiotherapy.

In 1903, «in recognition of his extraordinary services for the discovery of spontaneous radioactivity he shared the Nobel Prize in Physics with the Curies. Curiously, Becquerel received half of the prize, and the Curies couple the other half in equal parts.

The 1903 Nobel Prize in Physics awarded by half to Pierre and Marie Curie, and by half to Henri Becquerel. Its name appears in the text of the reward given to the couple.

He also did research on phosphorescence, spectroscopy, and light absorption.

His works include:

Research on phosphorescence (1882-1897)
Discovery of the invisible radiation emitted by uranium (1896-1897)...

Images

Henri Becquerel (1903).	Pechblenda polished section.	Photographic paper impressed by the radiation of the pechblenda of the previous image.	Image of a photo iron of Henri, which was exposed to radiation from a uranium salt. The shadow of the Malta cross placed between the plate and uranium salt is clearly seen.	Becquerel in his lab.

Acknowledgments

Rumford Medal (1900)
Medalla Helmholtz (1901)
Nobel Prize in physics shared with Pierre and Marie Curie (1903).
Medalla Barnard (1905)

Eponymy

In his honor a radioactive activity measure unit was baptized in the International Unit System: The Bequerelio
In his honor, the Becquerel crater has also been named on the Moon, and the Becquerel crater of Mars.
The asteroid (6914) Becquerel carries this name in his memory.

In his honor the becquerelita mineral was baptized.

Flora
Species

(Asteraceae) Cousinia becquereli Parsa
(Lamiaceae) Platostoma becquerelii Suddee " A.J.Paton

Description of his experiments to the French Academy of Sciences

This is how Becquerel described his experiments to the French Academy of Sciences on February 27, 1896:

One wraps a Lumière photographic plate with a bromide emulsion in two very thick black paper sheets, so the plate will not be watched when 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 everything to the sun for several hours. When the photographic plate is developed, it is recognized that the silhouette of the phosphorescent substance appears in black on the negative. If placed between the phosphorescent substance and paper a coin or a perforated metal screen with a trimmed design, it is seen that the image of these objects appears in the negative... Of these experiments we must conclude that the phosphorescent substance in question emits rays that pass through the opaque paper and reduce the silver salts.

But other experiments led him to doubt and later abandon this hypothesis. On March 2, 1896 he reported:

I insisted in particular on the following fact, which seems to me quite important and beyond the phenomena that could be expected to observe: The same crystalline crusts [of potassium sulfate uranile], arranged in the same way with respect to the photographic plates, in the same conditions and through the same screens, but protected from the excitation of the photographic rays incidents and maintained in the dark, still produce the same images. This is how they led me to make this observation: among the previous experiments, some had been prepared on Wednesday 26 and Thursday 27 February, and as the sun only went out intermittently these days, I kept the appliances prepared and returned the cases to the darkness of a office drawer, leaving instead the crusts of uranium salt. Since the sun did not come out in the following days, I reveloped the photo plates on March 1, hoping to find the very weak images. Instead, the silhouettes appeared with great intensity... A hypothesis that occurs to the mind naturally would be to assume that these rays, whose effects have a great similarity with the effects produced by the rays studied by M. Lenard and M. Röntgen, are invisible rays emitted by phosphorescence and persist infinitely longer than the duration of the luminous rays emitted by these bodies. However, current experiments, without being contrary to this hypothesis, do not justify this conclusion. I hope that the experiments that I am carrying out at this time can provide some clarification to this new kind of phenomena.

Writings

Becquerel, AH (1899). Cours de physique. Ecole Polytechnique, 1ère division, 2e année d'études,. 2. 1899-1900 (in French). Ecole Polytechnique. Consultation on 24 May 2022.
Becquerel, AH (1898). Cours de physique. Ecole Polytechnique, 2nd division. 3. 1898-1899 (in French). Ecole Polytechnique. Consultation on 24 May 2022.
Recherches sur les variations des spectres d'absorption dans les cristaux (1888) (in French)
Electro-Chimie (1882) (in French)
Travaux de physique optique et de radiographie. (1896-1900) (in French)
Sur leraynnement de l'uranium et sur diverses propriétés physiques duraynement des corps radioactifs (1900) (in French)
Sur une propriété nouvelle de la matière, la radio-activité: Conférence faite à Stockholm le 11 décembre 1903 (in French)

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