Notes of the video
https://drive.google.com/file/d/1Gs0u...

long Derivation
https://ecee.colorado.edu/~bart/book/...

Classical Free electron Theory Assumptions Success,Drawbacks, Drude
   • Classical Free electron Theory Assump...  

Kronig Penney Model Bands in Solids K P Model
   • Kronig Penney Model Bands in Solids K...  

E-k Diagram, Difference Between Direct Indirect band gap (DBS IBS)
   • E-k Diagram, Difference Between Direc...  

What is Density of States (DOS)
   • What is Density of States (DOS). Deri...  

Effective mass in semiconductor
   • Effective mass in semiconductors, Der...  

Probability of Occupation, Fermi Energy, Fermi Level, Fermi Dirac Distribution Function
   • Probability of Occupation, Fermi Ener...  

What is Phonon
   • What is Phonon in Solid state Physics...  


Free electron theory was given to explain the properties of solids. The fundamental assumption was electron moves in a constant potential well.
The free electron theory was successfully explained the electric conductivity and thermionic emission of metals.
But it failed to explain the classification of materials as solids, insulators and semiconductors.
To solve this problem the basic assumption of free electron theory was modified by Bloch.
Bloch proposed that the electron inside the material are not in constant potential but they are moving in periodic potential well as per the periodicity of lattice.
Kronig and Penney define the periodic one dimensional square potential well (they gave the shape of square potential well).
They explained mainly band in solids and classification of semiconductor and insulators.