In which type of electron emission, the electrons use high speed electrons to emit from the surface?

Concept:

The liberation of electrons from the surface of a metal is known as Electron Emission.

The minimum energy required by an electron to just escape (i.e. with zero velocity) from metal's surface is called Work function (W₀) of the metal.

There are basically four methods of producing electron emission,

1. Thermionic emission

2. Photoelectric emission

3. Field Emission

4. Secondary emission.

Thermionic Emission: In this type, the metal is heated to a sufficient temperature to enable the free electrons to come out of its surface.

Field Emission: In this type, a very strong electric field is applied to the metal which pulls the electrons out of the surface due to the attraction of the positive field.

Photoelectric Emission: In this type, the light of a certain frequency is made to fall on the metal surface which leads to the emission of electrons.

Secondary Emission: In this type, electrons emit from the surface by bombardment of high speed electron.