Publish On: 2019-05-16

Steeb more

Total Post: 416

Question: Describe cathode ray tubes

Reply On: 2014-01-07

lala singh

Total Post: 22

ANS: Describe cathode ray tubes

The fact that cathode rays are really elections traveling at high speed away from the cathode is made use of in instruments such as television tubes and cathode-ray oscilloscopes. The oscilloscope tube was first developed by the physicist Braun in 1897. Cathode rays from the thermionic cathode C pass through a small hole in a control grid and are accelerated by the voltage applied to the anode A. the electrons then pass between two pairs of parallel plates to which various test voltage may be applied. One pair of platesV, is horizontal; the other, H, is vertical. The electric fields of these plates therefore cause deflections, either vertically or horizontally in proportional to the values of the test voltages applied. The sport of light on the fluorescent screen S at the large end of the tube can travel around with extraordinary rapidity, because of the very small mass of the electrons and there high speeds. Hence these tubes can be used to follow transient variations of voltage, which are entirely too high frequency for any mechanical device to follow.   

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