Question

In a cathode ray tube, state:
A) The purpose of covering cathode by thorium and carbon.
B) The purpose of the fluorescent screen.
C) How is it possible to increase the rate of emission of electrons?

Answer 1

Hint: The cathode ray tube or CRT is a vacuum tube containing one or more weapons and a phosphorous monitor and is used to view images. This vacuum tube contains a single gun or two. It modulates, accelerates, and discharges onto the screen electron beams to create the images.

Complete step by step solution:
The CRT is a picture display in the shape of a video signal. It is a vacuum tube which shows images if the beam is struck on the phosphorescent surface through electron guns. With other words, the CRT generates the beams, speeds it up and distracts to produce the phosphorous images to make the beam visible.

The functioning of CRT depends on electron beam movement. The electron guns are used to generate high-voltage, sharply focused electrons. This high speed electron beam creates a light spot when it strikes the fluorescent screen.
1. In a Cathode Ray Tube the Purpose of Covering Cathode by Thorium and Carbon is to reduce the work function and decrease the melting point.

2. When an electron beam strikes the screen it gives a bright spot on it due to the fluorescence of the material coated on it.

3. On increasing the filament current, the rate of emission of electrons from the cathode will increase.

Note: The passage of the electron horizontally and vertically is independent of each other and the beam is located everywhere on the screen. The working parts of a CRT are contained in a glass vacuum cover to ensure easy movement of the emitted electron from one end of the tube to another.