Cathode ray tube works on the principle of (i) thermionic emission (ii) deflection of electron beam by the electric and magnetic fields and(iii) flourescence produced by the electron beam on the flourescent screen.
The cathode ray tube (CRT) is a vacuum tube containing an electron gun and a fluorescent screen, with internal or external means to accelerate and deflect the electron beam, used to form images in the form of light emitted from the fluorescent screen. The image may represent electrical waveforms (oscilloscope), pictures (television, computer monitor), radar targets and others.
The single electron beam can be processed in such a way as to display moving pictures in natural colors.
The CRT uses an evacuated glass envelope which is heavy, large, deep, and relatively fragile. Display technologies without these disadvantages, such as flat plasma screens, liquid crystal displays, DLP, OLED displays have replaced CRTs in many applications and are becoming increasingly common as costs decline.
An exception to the typical bowl-shaped CRT would be the flat CRTs used by Sony in their Watchman series. One of the last flat-CRT models was the FD-120A. The CRT in these units was flat with the electron gun located roughly at right angles below the display surface thus requiring sophisticated electronics to create an undistorted picture free from effects such as keystoning.
http://electronicstopics.blogspot.com/2008/10/cathode-ray-tube.html [1]
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[1] http://electronicstopics.blogspot.com/2008/10/cathode-ray-tube.html