X Ray
X Ray, penetrating electromagnetic radiation, having a shorter wavelength than light, and produced by bombarding a target, usually made of tungsten , with high-speed electrons. X rays were discovered accidentally in 1895 by the German physicist Wilhelm Conrad Roentgen while he was studying cathode rays in a high-voltage, gaseous-discharge tube. Despite the fact that the tube was encased in a black cardboard box, Roentgen noticed that a barium-platinocyanide screen, inadvertently lying nearby, emitted fluorescent light whenever the tube was in operation. After conducting further experiments, he determined that the fluorescence was caused by invisible radiation of a more penetrating nature than ultraviolet rays (see Ultraviolet Radiation ). He named the invisible radiation “X ray” because of its unknown nature. Subsequently, X rays were known also as Roentgen rays in his honor. X rays are electromagnetic radiation ranging in wavelength from about 100 A to 0.01 A (1 A is equivalent to ab