\u3ci\u3ePhysics\u3c/i\u3e, Chapter 43: X-Rays

The study of the electric discharge through gases led directly to the discovery of x-rays by W. C. Roentgen in 1895. While operating a gas discharge tube, Roentgen observed that a platinum-barium cyanide screen at some distance from the tube fluoresced. He shielded the tube so that no visible radiation could reach the screen, but the fluorescence could still be observed. On interposing various materials between the tube and the screen, he found that the intensity of the fluorescence could be diminished, but that it was not completely obliterated. He interpreted these observations as being due to radiation coming from the walls of the tube which penetrated the absorbing screens and caused the screen to fluoresce, and he called the new radiation x-rays to indicate their unknown character. The x-rays were produced when the cathode rays struck the glass walls of the electric-discharge tube