Electronics. A vaccum tube in which electrons are accelerated by high-voltage cathodes, formed into a beam by focusing electrodes, and projected toward a phosphorescent screen. The beam of electrons leaves a bright spot wherever it strikes the phosphor screen. To form a display on the screen, the electron beam is deflected in the vertical and horizontal directions either by electrostatical deflection plates or by the magnetic field produced by a coil located around the neck of the tube. Cathode ray tubes are used in computer monitors, television sets, oscilloscopes, and radar displays.