The Discovery of Radioactivity I. History leading up to the Discovery of Radioactivity Our story starts in the evening of November 8, 1895. He realized the importance of his discovery at once. He stayed up all night doing experiments and even ate and slept in the laboratory for a time. Although there is much more to be said about the discovery of X-rays, that will wait until another day. It appeared that the X-rays were coming from the glass walls of a cathode ray tube that was made fluorescent by the impact of the cathode rays.
Phosphorescence is the light continuing to be emitted after the external stimulus ceases.
Becquerel was the ideal man to follow up on this suggestion. His father had been the leading authority on phosphorescence for many years. Henri himself was an expert in the study of phosphorescence as well as photography. Also, he had already studied the phosphorescence of some uranium compounds. So, quite naturally, Becquerel brought his expertise to bear on the problem.