Cathode rays are invisible radiation emitted (given off) by one of the electrodes in a Crookes tube (see Crookes tube ). An electrode is a metal structure that conducts electric current. A Crookes tube contains two electrodes, the cathode and the anode. When a strong electric current flows from the cathode towards the anode, the cathode emits rays. Part of the glass of the tube is coated, usually with zinc sulfide. Where cathode rays strike the coating, the coating emits yellowish-green light. When a metal plate is placed in the path of the rays, a boldly defined shadow is created in the light at the end of the tube. Cathode-ray tubes are used in older television sets, computer monitors, radar displays, and scientific instruments.
Cathode rays are streams of electrons emitted at high speeds from the surface of the cathode. These cathode rays are identical with beta rays that are emitted by radium and other radioactive elements.
See also Fluorescence ; X rays .
