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'''Cathode ray tube''' or CRT is a vacuum tube device used to display graphic information on a screen (as opposed to performing purely electronic operations such as amplifying, oscillating, or switching). It is distantly descended from the [[Crooke's tube]].
'''Cathode ray tube''' or CRT is a vacuum tube device used to display graphic information on a screen (as opposed to performing purely electronic operations such as amplifying, oscillating, or switching). It is distantly descended from the [[Crooke's tube]].
In a cathode ray tube, a series of electrodes produces a narrow, tightly focussed beam of electrons. This beam is then deflected horizontally or vertically, either by other electrodes or by external magnetic fields. The beam travels a distance, typically on the order of one or two feet, and strikes a flat screen covered with phosphors. The phosphors glow where the beam strikes, causing a bright dot of light.