Crookes tube

Crookes tube, tube developed by English scientist Sir William Crookes to demonstrate the properties of cathode rays. A current, passed between metal electrodes in the tube, produces a glowing discharge, which disappears as the pressure is lowered. Cathode rays (beams of electrons) are then produced, striking the walls of the tube and causing it to glow. Experimenting with such a tube, Wilhelm Roentgen discovered X-rays.

See also: Cathode ray; Crookes, Sir William.