CATHODE RAY

stream of electrons leaving the negative electrode (cathode) in a discharge tube containing a gas at low pressure, or electrons emitted by a heated filament in certain electron tubes. Cathode rays focused on a hard target (anticathode) produce X rays or focused on a small object in a vacuum generate very high temperatures (cathode-ray furnace). Cathode rays cause phosphors to luminesce. This effect, when coupled with the controlled deflection of a cathode ray by electric or magnetic fields, gives rise to the cathode-ray oscilloscope (cathode-ray tube) for monitoring variations and values of an alternating voltage or current and to the picture tube of television and radar. Electrons emitted by radioactive nuclei are known as b-rays.