Electron Emission Interview Questions and Answers:

1. What is Fermi level?

Ans. The maximum energy that an electron in a metal has at the absolute zero temperature is called the Fermi level of energy and is designated by E_F.

2. What is an electron emission?

Ans. The liberation of electrons from the surface of a substance is known as electron emission.

3. What is meant by work function of a metal?

Ans. The work function, Φ or E_w, of a metal may be defined as the difference between the energy required to move an electron of a metal to an infinitely large distance and the maximum energy an electron can have at absolute zero temperature?

4. What is meant by thermionic emission?

Ans. The process of electron emission from the surface of metal into the surrounding space by heating the material is known as thermionic emission.

5. What is meant by photoelectric emission?

Ans. When the surface of certain alkaline material such as sodium, potassium, cesium, or rubidium is illuminated by a beam of light or ultraviolet radiations, the electrons are emitted. This phenomenon is called the photoelectric emission.

6. What is meant by the threshold frequency?

Ans. The minimum frequency which can cause photoelectric emission is called the threshold frequency.

7. On what factors does the utility of a particular material as an emitter depend?

Ans. The usefulness of a particular material as an emitter depends on (i) emission efficiency (ii) mechanical strength (iii) longevity at normal operating temperatures and (iv) stability of its surface under normal working conditions.

8. Why do directly heated cathodes introduce hum in the circuit?

Ans. Any variation in heating voltage affects the electron emission and thus introduces hum in the plate circuit.