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प्रश्न
Why are materials of low work function preferred as thermionic cathode materials?
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उत्तर
By using materials of low work functions, the emission of electrons from such a surface takes place at relatively low temperature (at 1700°C in instead of 2500°C approximately).
संबंधित प्रश्न
An electromagnetic radiation is used for photography in fog. [2]
(i) Identify the radiation.
(ii) Why is this radiation mentioned by you, ideal for this purpose ?
Draw a diagram of a simple atom showing the nucleus and electrons. In this atom:
(a) What type of charge will there be on the nucleus?
(b) What is the value of this charge?
A radioactive substance is oxidized. What changes would you expect to take place in the nature of radioactivity? Explain your answer.
What is meant by Radioactivity?
A certain nucleus has a mass number 20 and atomic number 9. Find the number of neutrons and protons present in it.
An electrons emitter must have how much work function and melting point.
From α, β and γ-rays, name the one which travels with the speed of light?
State three ways of obtaining an electron-beam.
Assertion (A): The force of repulsion between atomic nucleus and α-particle varies with distance according to inverse square law.
Reason (R): Rutherford did α-particles scattering experiment.
