JEE Main & Advanced Physics Semiconducting Devices Electron Emission from Metal

Electron Emission from Metal

Category : JEE Main & Advanced

(1) Free electron in metal experiences a barrier on surface due to attractive Coulombian force.

(2) When kinetic energy of electron becomes greater than barrier potential energy (or binding energy\[{{E}_{b}}\]) then electron can come out of the surface of metal.

(3) Fermi energy \[({{E}_{f}})\]: Is the maximum possible energy possessed by free electron in metal at 0K temperature

(i) In this energy level, probability of finding electron is 50%.

(ii) This is a reference level and it is different for different metals.

(4) Threshold energy (or work function \[{{W}_{0}}\]) : Is the minimum energy required to take out an electron from the surface of metal. Also \[{{W}_{0}}={{E}_{b}}{{E}_{f}}\]

 

 

Work function for different materials \[{{({{W}_{0}})}_{\text{Pure tungsten}}}\text{ }\!\!~\!\!\text{ }~=\text{ }4.5eV\]

\[{{({{W}_{0}})}_{\text{Throated tungsten}}}~=\text{ }2.6eV\] \[{{({{W}_{0}})}_{\text{Oxide coated tungsten}}}=\text{ }1eV\]

 

(5) Four processes of electron emission from a metal are

(i) Thermionic emission        

(ii) Photoelectric emission 

(iii) Field emission 

(iv) Secondary emission  

Other Topics



LIMITED OFFER HURRY UP! OFFER AVAILABLE ON ALL MATERIAL TILL TODAY ONLY!

You need to login to perform this action.
You will be redirected in 3 sec spinner

Free
Videos