Physics — Winter 2025

Prove that Probability of occupancy of Fermi energy level is 0.5 at T > 0 K

Explain how the materials are classified into conductors, semiconductors and insulators with the help of energy band diagrams.

Explain in detail how Kroning and Penney model explains the origin of band gap in semiconductors.

Define Following Terms

Population Inversion , (ii) Meta stable state (iii) Active Medium

Define carrier transport and explore how charge carriers move within semiconductor materials, emphasizing the mechanisms of drift and diffusion.

Describe how to formulate the density of holes in the valence band for intrinsic semiconductors.

Describe the definition of carrier concentration in intrinsic semiconductors and show how to derive the formula for electron density in the conduction band.

Determine the band gap of the material when the light source composed of it emits radiation with a wavelength of 8628 Å.

Explain construction and working of PV solar cell.

Interpret the process of deriving the Fermi level expression for n-Type semiconductors, and subsequently, utilize this expression to compute the electron density in the conduction band.

The intrinsic carrier concentration at room temp in Germanium is 4.17×1018 m-3. The mobility of Electron and Hole are 0.29 m2/VSec and 0.16 m2/vSec respectively. Find out its Resistivity

The conductivity of a semiconductor at 30 ℃ is 742 Ʊ/m and at 90 ℃ is 2100 Ʊ/m. Calculate the Energy Band Gap.

Discuss the Einstein’s theory about interaction between matter and radiation in detail. Also discuss the absorption and emission with necessary equation.

A Silicon plate of thickness 1mm, breadth 10 mm and length 100 mm is placed in a magnetic field of 0.5 Wb/m2 acting along its thickness. If 0.01 A1 current flows along its length, calculate the Hall coefficient if developed Hall voltage is 1.83 mV.

Discuss in detail Four probe method used for resistivity measurements in thin sheet.

Define density of states and obtain expression for the density of states in terms of mass of electron(m), Planck’s constant (h) and Energy (E).

What is hot point probe method? Explain

List the condition to be satisfied to use Vander Pauw technique and derive expression of bulk resistivity measurement using it.

What is Band gap? How can we use UV-VIS spectroscopy for band gap measurement for semiconductors explain in detail.

Distinguish between Type-Iand Type-II Superconductivity

The Fermi level in given material is 2.8 eV. What are the energies for which the probabilities of occupancy at 270K are 0.89,0.20, 0.02 and 0.5

(i) Discuss BCS theory of superconductivity in brief (ii)What is cryotron? Discus

Explain the Fermi’s Golden Rule in brief.

The critical magnetic field of a given superconductor is 9.5 x 10^3 A/m at 0 K. At what temperature does the critical magnetic field of the sample drop to 5 x 10^3 A/m, given that the critical temperature of the sample is 7.2 K? Also, calculate the critical current density at that temperature if the radius of the wire is 0.4 mm.

List various properties of Superconductors and explain them in detail.