# MS Solid State Physics Past Paper 2020 Punjab University

## For a pure semiconductor, the Fermi level is

1. In the valence band
2. In the conduction band
3. Well below the valence hand
4. Near the center of the gap between the valence and conduction bands

Correct Option: (D)

The Fermi level is the energy level at which the probability of finding an electron is 50%.

The Fermi level for a pure semiconductor is near the center of the gap between the valence and conduction bands.

Semiconductor type Fermi level location
Intrinsic semiconductor Near the center of the band gap
n-type semiconductor Closer to the conduction band
p-type semiconductor Closer to the valence band

## An acceptor replacement atom in silicon might have – – – electrons in its outer shell

1. 3
2. 4
3. 5
4. 6

Correct Option: (A)

An acceptor replacement atom in silicon has 3 electrons in its outer shell because it needs 1 more electron to complete its valence shell.

This electron will come from a neighboring silicon atom creating a hole in the valence band of the silicon atom.

## Quarks are the constituents of

1. All leptons
2. All particles
3. Only strange particles
4. All strongly interacting particles

Correct Option: (D)

Quarks are the constituents of all strongly interacting particles.

## Nuclear fusion in the Sun is increasing its supply of

1. Helium
2. Nucleons
3. Positrons
4. Hydrogen

Correct Option: (A)

Nuclear fusion in the Sun is decreasing its supply of hydrogen and increasing its supply of helium.

The hydrogen nuclei fuse together to form helium nuclei releasing a tremendous amount of energy.

## A three-dimensional array of points each of which has identical surroundings is called a

1. Motif
2. Unit cell
3. Space lattice
4. Lattice points

Correct Option: (B)

A three-dimensional array of points each of which has identical surroundings is called a unit cell.

## Which of the following is not a property of crystalline solids

1. Isotropy
2. Anisotropy
3. Definite geometry
4. Sharp melting point

Correct Option: (A)

## The space lattice of a diamond is fcc. The primitive basis has two identical atoms at

1. $$000, \frac{1}{2}\frac{1}{2}0$$
2. $$000, \frac{1}{4}\frac{1}{4}\frac{1}{4}$$
3. $$000, \frac{1}{2}\frac{1}{2}\frac{1}{2}$$
4. $$000, \frac{1}{4}\frac{1}{4}\frac{3}{4}$$

Correct Option: (B)

## A relation between the surface integral of a vector and the volume integral of a derivative of the vector is

1. Gauss’ law
2. Stoke’s theorem
3. Gauss’s theorem
4. Convolution theorem

Correct Option: (C)

A relation between the surface integral of a vector and the volume integral of a derivative of the vector is Gauss’s theorem.

$\oint_{S}^{} \overrightarrow{A} .\overrightarrow{ds} = \oint_{V}^{} (\overrightarrow{\nabla } . \overrightarrow{A})dV$

## The effective mass is used to measure the

1. Barrier concentration
2. Carrier concentration
3. Fermi energy
4. None of these

Correct Option: (B)

The effective mass is used to measure the carrier concentration.

## If the resistivity (Ω-cm) is in the range of 108 to 1020 then the material is a

1. Insulator
2. Conductor
3. Semiconductor
4. Superconductor