Physics — Winter 2024

Define: (1) Valance Band (2) Current density (3) Fermi Function

Distinguish between Direct energy band gap semiconductor and Indirect energy band gap semiconductor with any four points.

Explain in details about Kroning-Penney model and discuss the different cases with necessary diagrams.

List out any six applications of Solar cell.

The energy gap of two intrinsic semiconductors Aand Bare 0.36 eV and 0.72 eV respectively. Compare the carrier density of semiconductors Aand Bat temperature 300 K.

Define density of holes in valence band and derive the necessary equation for it.

(1) State and prove the Law of Mass Action. (2)Define Luminescence and categories them with suitable illustrations.

Distinguish between Spontaneous Emission and Stimulated emission with any three points.

Define Exciton and classify them in details.

Derive the expression for Fermi energy and carrier concentration in N-type semiconductor.

Distinguish between N-type semiconductor and P-type semiconductor with any four points.

What are the processes known as carrier generation and recombination? Explain the Optical Generation and recombination process for charge carriers.

Derive the relation between Einstein’s coefficients and interpret the results.

Define: (1) Superconductivity (2) Critical Temperature (3) Cooper pair

The values of critical magnetic field for a superconductor are 270 Tand 60 Tat temperature 20 Kand 90 Krespectively. Calculate the values of critical temperature and zero magnetic field.

Define density of state and derive the necessary formula for DOS.

Name the types of capacitances are associated with PN junction and briefly explain each of them.

Explain the Hot Point Probe method to verify the type of extrinsic semiconductors.

Explain the Four Probe method and derive the necessary formula to find the resistivity of Balk material.1

Distinguish between type-Isuperconductor and type-II superconductor.

For a metal having density of electron is 6.5 × 1028 then find the relaxation time of conduction electrons if the metal resistivity is 1.435 × 10-8 ohm-meter

Explain the Vander Pauw measurement method. Discuss about the measurement of Resistivity of the material by this method.

What is Drude Model? List out the basic assumptions of Drude Model.

Discuss about Meissner’s effect with diagrams and prove that the superconductors are perfect diamagnetic material.

(1) What is Josephson’s Junction? Explain the types of Josephson’s effect. (2) Calculate the Critical magnetic field and Critical Current for a superconducting wire of Lead having a diameter of 1 mm at 4.2 K. Critical temperature of lead is 7.18 k and zero magnetic field is 65 kA/m.