Wilhelm Roentgen of Germany, while conducting experiments with cathode rays, accidentally discovers a new and different kind of ray. These rays were so mysterious that Roentgen named them "x-rays." He received the first Nobel Prize in Physics in 1901 for this discovery.
French physicist Antoine Henri Becquerel's experiments led to the discovery of radioactivity. He observed that the element uranium can blacken a photographic plate, even though separated from it by glass or black paper. He also observed that the rays that produce the darkening are capable of discharging an electroscope, indicating that the rays possess an electric charge.
J. J. Thomson of Britain discovers the electron, while also studying cathode rays. He received the Nobel Prize in Physics in 1906 for this discovery.
Ernest Rutherford discovers two kinds of rays emitting from radium. The first he calls alpha rays; the more penetrating rays he calls beta rays.