Whenever we study or talk about radio activity, the name Henri Becquerel at once clicks to our minds. He was the discoverer of radioactivity, for which he also won the 1903 Nobel Prize in Physics.
Antoine Henri Becquerel was born in Paris on December 15, 1852, a member of a distinguished family of scholars and scientists. His father, Alexander Edmond Becquerel, was a Professor of Applied Physics and had done research on solar radiation and on phosphorescence. He entered the Polytechnic in 1872 and ultimately became a professor in the same institute of the Applied Physics.
The early research of Becquerel was almost entirely in optics. His first extensive investigations dealt with the rotation of plane-polarized light by magnetic fields. He next turned to infra-red spectra, making visual observations by means of the light released from certain phosphorescent crystals under infra-red illumination. He then studied the absorption of light in crystals. With these researches, Becquerel obtained his doctorate from the Faculty of Sciences of Paris in 1888 and election to the Academy of Sciences in 1889. Thus at the age of forty-three, Becquerel was established in the rank and liability, his years of active research behind him and all that for which he is still now remembered.
Talking about the invention of radioactivity Becquerel decided to investigate whether there was any connection between X-rays and naturally occurring phosphorescence. The glow of X-ray emission put Becquerel in mind of the light in his study although he had not done much active research in the last few years. He had inherited from his father a supply of uranium salts, which react when exposed to light. When the salts were placed near to a photographic plate covered with opaque paper, the plate was discovered to be fogged.
The phenomenon was found to be common to all the uranium salts studied and was concluded to be a property of the uranium atom. Finally, Becquerel showed that the rays emitted by uranium caused gases to ionize and that they differed from X-rays in respect that they could be deflected by electric or magnetic fields. In this way his spontaneous discovery of radioactivity took place as like most physicists; he had a better understanding of the nature of matter that brought him closer to reaching this final philosophical goal.
Nowadays it is generally considered that Becquerel discovered radioactivity by chance, but it is truer to say that he was looking for an effect so similar to radioactivity that he must have discovered it sooner or later, and he was so great a scientist that he quickly realized the importance of his evidence. It is also known that Becquerel discovered one type of radioactivity beta particles which is due to high-speed electrons leaving the nucleus of the atom.
Becquerel also authored the detailed studies of the physical properties of cobalt, nickel and ozone, studied how crystals absorb light, and researched the polarization of light. He is the namesake of the Becquerel, the basic unit of radioactivity used in the international system of radiation units, referred to as “SI” units. From handling radioactive stones he developed serious and recurring burns on his skin, which may have been a contributing factor in history.
Besides being a Nobel Laureate, Becquerel was elected a member of the Academe des Sciences de France and succeeded Berthelot as Life Secretary of that body. He was a member also of the Accademia dei Lincei and of the Royal Academy of Berlin, amongst others. He was also made an Officer of the Legion of Honour. Becquerel published his findings in many papers, principally in the Annales de Physique et de Chimie and the Comptes Rendus de l’Academie des Sciences.
This famous scientist died in 1908 at Croissic in Britanny and is still remembered to date among the outstanding Physicists.
