Henri Becquerel early work

The plane polarization of light was the concern Becquerel's earliest work, with the absorption of light by crystals and with the phenomenon of phosphorescence. Terrestrial magnetism was also a subject he worked on. In 1896, his discovery of phenomenon of natural radioactivity overshadowed his previous work. Becquerel decided to investigate whether there was any connection between X-rays and naturally occurring phosphorescence, after discussing with Henri Poincaré on the radiation which had recently been discovered by X-rays and which was accompanied by a type of phosphorescence in the vacuum tube. He inherited, from his father, a supply of uranium salts, which phosphoresce on exposure to light.