Solve your IGNOU Doubts

Question:

The saturation magnetization of $fcc\text{ Ni}$ is $5.1 \times 10^5\text{ A/m}$ . If the lattice constant for $\text{Ni}$ is $3.52\text{ \AA}$ , calculate the net magnetic moment per $\text{Ni}$ atom in the crystal in units of Bohr magnetons.

See Answer →

Question:

A metal has an fcc structure, a lattice parameter $a = 0.4\text{ nm}$ , and a valence $Z = 1$ . Calculate its Hall coefficient.

See Answer →

Question:

A monovalent metal has a bcc structure and its lattice parameter is $1.5\text{ \AA}$ . Calculate its Fermi energy.

See Answer →

Question:

In a p-n junction in Si, $N_d = N_a = 10^{22}\text{ m}^{-3}$ . Calculate the built in potential for Si at $300\text{ K}$ if n_i for Si at $300\text{ K} = 10^{16}\text{ m}^{-3}$ .

See Answer →

Question:

Consider a superconductor with an energy gap of $1.7 \times 10^{-4}\text{ eV}$ . Find the maximum wavelength of electromagnetic radiation which will be absorbed by this superconductor.

See Answer →

Question:

The values of the elastic stiffness constants for $\text{GaAs}$ are:

$C_{11}=1.18\times 10^{11}\\mathrm{N\,m^{-2}},\quad C_{44}=0.59\times 10^{11}\\mathrm{N\,m^{-2}}\quad\text{and}\quad C_{12}=0.54\times 10^{11}\\mathrm{N\,m^{-2}}.$
Given that the density of $\text{GaAs}$ is $5.32\text{ g cm}^{-3}$ , determine the bulk modulus of elasticity and the velocity of the transverse and longitudinal elastic waves in the [100] direction.

See Answer →

Question:

Calculate the Debye specific heat of copper at $300\text{ K}$ , given that its Debye frequency is $4.11 \times 10^{13}\text{ rad s}^{-1}$ .

See Answer →

Question:

The frequency of the longitudinal optical phonon for $\text{NaCl}$ at the centre of the first Brillouin zone is $5\text{ rad s}^{-1}$ . Calculate the interatomic force constant for this material. (The atomic weight of $\text{Na} = 23$ and $\text{Cl} = 37$ )

See Answer →

Question:

The potential energy of the Neon crystal is described by the expression:

$$U(r) = -4\varepsilon \left[ \left( \frac{\rho_0}{r} \right)^6 - \left( \frac{\rho_0}{r} \right)^{12} \right]$
where $\varepsilon = 3.12 \times 10^{-3}\text{ eV}$ and $\rho_0 = 2.82\text{ \AA}$ . Calculate the lattice parameter of the Neon crystal (fcc structure).

See Answer →

Question:

The potential energy of the Neon crystal is described by the expression:

$$U(r) = -4\varepsilon \left[ \left( \frac{\rho_0}{r} \right)^6 - \left( \frac{\rho_0}{r} \right)^{12} \right]$

See Answer →

Question:

Show that the reciprocal lattice for an fcc lattice is a bcc lattice. If the lattice constant of the unit cell of the fcc lattice is a, determine the lattice constant for the unit cell of the reciprocal bcc lattice?

See Answer →

Question:

The Bragg angle for reflection from the (110) planes in bcc iron is $22^{\circ}$ for an x-ray of wavelength $1.54\text{ \AA}$ . Find the cube edge for iron (take $n = 1$ ). What is the minimum wavelength with which the structure of this unit cell can be probed?

See Answer →

Question:

Sodium metal crystallizes in the bcc structure. The metal has atomic weight 23 and density $971\text{ kg m}^{-3}$ . Calculate the cubic lattice parameter a and the shortest distance between atoms in this structure.

See Answer →

Question:

A plane intercepts the x-axis at 3a, the y-axis at 2b and the z-axis at 4c. Determine the Miller indices of this plane.

See Answer →

Question:

What is the function of the quartz crystal used in a digital watch?

See Answer →

Question:

In which of the following ions do you expect angular momentum quenching and why:

$$\text{Ti}^{3+}, \text{Gd}^{3+}, \text{Ni}^{2+}$

See Answer →

Question:

What is the probability that a donor atom at energy E_D is ionized?

See Answer →

Question:

The Fermi energy for silver is $5.48\text{ eV}$ . Which of the following is true : (a) the density of energy states is greater at $2\text{ eV}$ (b) the density of energy states is greater at $6\text{ eV}$ or (c) the density of energy states is same near both energies?

See Answer →

Question:

Is the following statement true for vibrations of a chain of two different types of atoms: “At the centre of the Brillouin zone, the frequency of the optical branch is less than the frequency of the acoustic branch”? Explain.

See Answer →

Question:

The electronic and lattice heat capacities for copper at $0.01\text{ K}$ are $5.04\times 10^{-6}\\text{J/(kmole-K)}$ and $4.60\times 10^{-11}\\text{J/(kmole-K)}$ respectively. What do you conclude from these magnitudes?