The device that provides the viewing screen in the television tube, the radar viewer, and the cathode-ray oscilloscope. The cathode-ray tube consists of an evacuated tube containing a heated cathode and two or more ring-shaped anodes through which the cathode rays can pass so that they strike the enlarged end of the tube (see illustration). This end of the tube is coated with fluorescent material so that it provides a screen. Any point on the screen that is struck by the cathode ray becomes luminous. A control grid between the cathode and the anode enables the intensity of the beam to be varied, thus controlling the brightness of the illumination on the screen. The assembly of cathode, control grid, and anode is called the electron gun. The beam emerging from the electron gun is focused and deflected by means of plates providing an electric field or coils providing a magnetic field. This enables the beam to be focused to a small point of light and deflected to produce the illusion of an illuminated line as this point sweeps across the tube.
The television tube is a form of cathode-ray tube in which the beam is made to scan the screen 625 times to form a frame, with 25 new frames being produced every second. (These are the figures for standard television tubes in the UK). Each frame creates a picture by variations in the intensity of the beam as it forms each line.
Cathode-ray tube
- luminous intensity
- lunar eclipse
- lunation
- lux
- Lyman series
- m.k.s. units
- m.m.f.
- Mach number
- Mach's principle
- machine
- Maclaurin's series
- macroscopic
- Magellanic clouds
- magic numbers
- Magnadur
- Magnalium
- magnet
- magnetic bottle
- magnetic bubble memory
- magnetic circuit
- magnetic compass
- magnetic constant
- magnetic containment
- magnetic declination
- magnetic dip