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The focusing anode ensures that the electrons emitted from the cathode in slightly different directions are focused down to a narrow beam and all arrive at the same spot on the screen. Hence, it controls the brightness of the spot on the screen. The control grid controls the flow of electrons between the cathode and the accelerating anode. The area where the electrons beam strikes the screen glows brightly. Electrons passing through the hole in the anode form a narrow beam and travel with constant horizontal velocity from the anode to the florescent screen. This potential difference generates an electric field between the accelerating anode and the cathode which accelerates electrons from cathode to accelerating anode. Cathode is a conductor that emits electrons from its surface when heated to a high temperature.Ī high positive voltage is applied to the accelerating anode of the order of 1 to 20,000 volts, relative to the cathode. The heater at the left side in the figure heats the cathode to a high temperature. They are: heater, cathode, control grid, accelerating anode, and focusing anode. The electron gun again internally consists of five components. The electron gun is used for generating, controlling and focusing the beam of electrons enclosed in a vacuum tube. Both the horizontal and vertical deflection plates controls the path of electrons beam so that it can be directed towards a specified positions on the phosphor-coated screen.įluorescent screen is a transparent screen coated on one side with a phosphor that glows brightly when exposed to cathode rays.