Explain the functions of the parts of a cathode ray tube?

This is a diagram of a cathode ray tube. It consists of 3 main parts:

• The Electron Gun
• The Deflection System
• The Fluorescent Screen

The electron gun is exactly what it sounds like. It basically produces electrons at a very high and precise velocity through thermionic emission.

At this point a filament in the cathode is heated until the electrons inside it become loose, allowing them to jump around. Then an anode of high voltage is applied to it. This directs the electrons toward the screen and accelerates them (creds to electrostatic attraction). While traveling toward the screen, the electrons cross an array of control grids. These grids monitor the brightness of the picture on the screen. The brightness depends on the negativity – the more electrons = the more negative the grid = the darker the image.

The deflection system is made up of two sets of electrical and magnetic fields, arranged perpendicularly to maintain control of both X and Y axes. The deflection system monitors the image that appears on the screen by controlling the position of the electrons that hit the screen.

The fluorescent screen shows where the electrons are colliding with the CRT. The screen has a coating usually made up of zinc sulphide or phosphorus which emits light where the electrons strike it.

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