What is Cathode ray tube?
[[File:Cathode ray Tube.PNG|right|thumb|300px|Cathode ray tube using electromagnetic focus and deflection (parts shown are not to scale)]] The '''cathode ray tube''' or '''CRT''' was invented by [[Karl Ferdinand Braun]]. It was the most common type of [[display device|display]] for many years. It was used in almost all [[computer monitor]]s and [[television]]s until [[LCD]] and [[plasma display|plasma screen]]s started being used.<ref>{{cite web|title=History of the Cathode Ray Tube|url=http://inventors.about.com/od/cstartinventions/a/CathodeRayTube.htm|publisher=about.com|accessdate=9 October 2013}}{{Dead link|date=January 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> A cathode ray tube has an [[electron gun]]. The [[cathode]] is an [[electrode]] (a metal that can send out [[electrons]] when heated). The cathode is inside a glass tube. Also inside the glass tube is an [[anode]] that attracts electrons. This is used to pull the electrons toward the front of the glass tube, so the electrons shoot out in one direction, making a [[cathode ray]]. To prevent gas discharge, which would prevent the tube from working, the air is taken out of the tube, making a [[vacuum]]. The electrons hit the front of the tube, where a [[phosphor]] screen is. The electrons make the phosphor light up. The electrons can be aimed by creating a magnetic field. By carefully controlling which bits of phosphor light up, a bright picture can be made on the front of the vacuum tube. Changing this picture 30 times every second will make it look like the picture is moving. Because there is a vacuum inside the tube (which has to be strong enough to hold out the air), and the tube must be glass for the phosphor to be visible, the tube must be made of thick glass. For a large [[television]], this vacuum tube can be quite heavy. The cathode ray tube was invented in 1897, and used as an [[oscilloscope]] (a machine to show waves). Later, along with other inventions and improvements, it was used for the first modern electronic televis