Fermi Energy

1) What is meant by Fermi Energy and Fermi Level?

Ans: In a metal, the quantised energy levels are filled up by free electrons in accordance with Pauli's exclusive principle. The energy of the highest occupied level at absolute zero temperature is called the fermi energy and the corresponding energy level is known as the Fermi level.

2) What is meant by Fermi factor?

Ans: The probabilityof finding an electron having an particular value of energy E at a temperature T is given by Fermi-Dirac probability distribution function.

3) What is meant by thermionic emmision and thermionic work function?

Ans: The phenomenon of emission of electrons from a metal surface by supplying thermal energy to the metal is called thermionic emmision.

According to quantum free electron theory at absolute zero temperature energy levels EF are filled and the energy levels above EF are empty.With the increase of temperature, the electrons are thermally exicted and move to higher energy states. The minimum energy that an electron should posses in order to come out of  the surface of a metal is called thermionic work function.