For many decades cathode-ray tubes, or picture tubes, were used to display TV pictures. Such sets turn the video signal into beams of electrons. The picture tube is rectangular at the front where the screen is and narrow at the back. Three electronic guns shoot electrons through the tube to the front of the screen, which is coated with phosphor. The beams paint thousands of dots on the screen to form the picture.

In the past decade LCDs and plasma displays have replaced the good old picture tube. They are much lighter and thinner because they do not have a big tube in them.

LCD screens have liquid crystal layers that can be controlled by an electric current. Millions of pixels on these layers can be either switched on or off. The crystals pass through color filters to produce millions of different colors.

A plasma television is made up two sheets of glass. Between them are millions of pixels filled with gas.

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Each pixel is coated with colored phosphor, red, green and blue. When electricity passes through, it causes the colored phosphor to produce light.


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beam = ray, line cathode-ray tube = object used in television screens and computers in which electrons produce an image on the screen cause = make coat = paint current = the flow of electricity decade = ten years display = show dot = point electricity = the power that is carried by wires and cables, and is used to give us light and heat electron = very small particle with a negative charge that moves around the centre of an atom liquid crystal display = screen that uses moving crystals to show a picture narrow = not wide phosphor = yellowish substance that starts to burn when it is in the air and shines in the dark pixel = dot on a screen rectangular = an object with four straight sides, two of which are usually longer replace = to be in something’s place sheet =layer switch = turn tube = part of a television that produces a picture on the screen