Attempt any five from the following

1(a)
Draw (a) (1 1 2) (b) (0 4 0) (c) [0 4 0] with reference to a cubic unit cell

3 M

1(b)
What is the probability of an electron being promoted to the conduction band in diamond at 27°C, if the bandgap is 5.6 eV wide?

3 M

1(c)
Define drift current, diffusion current and mobility of charge carriers.

3 M

1(d)
What is dielectric polarization and dielectric susceptibility? Write the relation between them.

3 M

1(e)
State and explain Ohm's law in magnetic circuit.

3 M

1(f)
Write Sabine's formula and explain the terms used in it.

3 M

1(g)
Calculate the length of an iron rod which can be used to produce ultrasonic waves of 20kHz Given - Y = 11.6 × 10

^{10}N/m^{2}, ρ = 7.23 × 10^{3}kg/m^{3}
3 M

2(a)
Explain formation of energy bands in solids and explain classification on the basis of energy band theory.

8 M

2(b)
Zn has hcp structure. The nearest neighbour distance is 0.27 nm. The atomic weight of Zn is 65.37. Calculate the volume of unit cell, density and atomic packing fraction of Zn.

7 M

3(a)
What is hysteresis? Draw a hyteresis for ferromagnetic material and explain various important parameters.

A magnetic material has a magnetization of 2300 A/m and produces a flux density of 0.00314 wb/m

A magnetic material has a magnetization of 2300 A/m and produces a flux density of 0.00314 wb/m

^{2}, Calculate magnetizing force and permeability of the material.
8 M

3(b)
Explain the statement 'crystal act as three dimesional grating with X-rays'.

Monochromatic X-ray beam of wavelength &lambda = 5.8189 A° is reflected strongly of lattice constant 3A°. Determine Miller indices of the possible reflecting planes.

Monochromatic X-ray beam of wavelength &lambda = 5.8189 A° is reflected strongly of lattice constant 3A°. Determine Miller indices of the possible reflecting planes.

7 M

4(a)
Define ligancy. Find the value of critical radius ratio for ligancy 4.

5 M

4(b)
An impurity of 0.01 ppm is added to Si. The semiconductor has a resistivity of 0.25Ωm at 300K. Calculate the hole concentration and its mobility. Atomic weight of Si is 28.1, density of Si=2.4×10

^{3}kg/m^{3}
5 M

4(c)
Explain the origin of electronic, ionic and orientational polarization and temperature dependence of respective polarizability.

5 M

5(a)
The density of copper is 8980kg/m

^{3}and unit cell dimension is 3.61 A°. Atomic weight of copper is 63.54. Determine type of crystal structure. Calculate atomic radius and interplanner spacing of (1 1 0) plane.
5 M

5(b)
What is Hall effect? Derive expression for Hall voltage with neat labelled diagram.

5 M

5(c)
Explain how the reverberation time is affected by (i) size (ii) nature of wall surface (iii) audience in an auditorium.

5 M

6(a)
Estimate the ratio of vacancies at (i) -119°C (ii) 80°C where average required to create vacancy is 1.8eV.

5 M

6(b)
How a p-n junction diode is used to generate a potential, difference in a photovoltaic solar cell?

5 M

6(c)
Explain with neat lebelled diagram the construction and working of a piezoelectric oscillator.

5 M

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