cathode-ray tube, special-purpose electron tube in which electrons are accelerated by high-voltage anodes, formed into a beam by focusing electrodes, and projected toward a phosphorescent screen that forms one face of the tube. The beam of electrons leaves a bright spot wherever it strikes the phosphor screen. To form a display, or image, on the screen, the electron beam is deflected in the vertical and horizontal directions either by the electrostatic effect of electrodes within the tube or by magnetic fields produced by coils located around the neck of the tube. Some cathode-ray tubes can produce multiple beams of electrons and have phosphor screens that are capable of displaying more than one color. Cathode-ray tubes are used in television sets, computer monitors, automated teller machines, oscilloscopes, and radar displays.

cathode, electrode through which current leaves an electric device. In electrolysis, it is the negative electrode in the electrolytic cell.

Electronic display device used to produce patterns on a screen that are the graphical representations of electrical signals. Time is normally on the horizontal axis, and a function of the voltage generated by the input signal to the oscilloscope on the vertical axis; four or more plots can be simultaneously shown. Because almost any physical phenomenon can be converted into a corresponding electric voltage, oscilloscopes find commercial, engineering, and scientific applications in acoustic research, television-production engineering, and electronics design.

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Stream of electrons leaving the negative electrode, or cathode, in an evacuated or gas-filled discharge tube or emitted by a heated filament in certain electron tubes. Cathode rays cause fluorescent materials to luminesce and are utilized in cathode-ray oscilloscopes and television tubes (see cathode-ray tube).

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Terminal or electrode at which electrons enter a system, such as an electrolytic cell or an electron tube. In a battery or other source of direct current, the cathode is the positive terminal. In a passive load it is the negative terminal. In an electron tube, such as a cathode-ray tube, electrons stream off the cathode and travel through the tube toward the anode.

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