8 nov 1896 ano - Wilhelm Conrad Roentgen

Descrição:

The discovery of radioactivity.

Upon further observation Wilhelm found that it originated from a partially evacuated Hittorf-Crookes tube, covered in opaque black paper which he was using to study cathode rays. He concluded that the fluorescence, which penetrated the opaque black paper, must have been caused by rays. This process has resulted in the discovery of X-rays.