Solve any five of the following.

1(a)
Identify the type of lattice and number of atoms per unit cell for CsCl and BaTiO

_{3}(above 120°C) crystal strcuture.
3 M

1(b)
Fermi Energy for Silver is 5.5 eV. Find out the energy for which the probability of occupancy at 300K is 0.9.

3 M

1(c)
Explain the formation of depletion region in an unbiased p-n junction.

3 M

1(d)
Write three distinct differences between ionic and oriental polarization.

3 M

1(e)
Draw the variation of permeability against external magnetic field for a paramagnetic and ferromagnetic material (below Curie temperature)

3 M

1(f)
Mention only one solution for each of the following acoustical problems in a hall. (i) Echo (ii) Dead spot and (iii) Inadequate loudness

3 M

1(g)
What is piezoelectric effect? Why ferro-electrics are prefferred than quartz for the production of ultrasonic waves?

3 M

2(a)(i)
What is effective mass? Why the effective mass of holes is more than the effective mass of electrons?

4 M

2(a)(ii)
Draw the diagrams only (fully labelled and self explanatory) to show the variation of Fermi energy with (i) Temperature and (ii) Impurity concentration at high level, for an n-type semiconductor.

4 M

2(b)
Define space lattice and basis. A metal crystallizes with a density of 2.7gm/cc and has a packing fraction of 0.74. Determine the mass of one atom if the nearest neighbour distance is 2.86Å.

7 M

3(a)
Explain the variation in magnetic induction with magnetic field for a ferromagnetic material, using the domain theory and with the help of a graph. A magnetic field of 1800 Amp/m produces a magnetic flux of 3×10

^{-4}Wb in an iron bar of cross-sectional area of 0.2cm^{2}. Calculate the susceptibility and the permeability.
8 M

3(b)(i)
How the variation in glancing angle is achieved while determining the crystal structure using (i) Rotating crystal method and (ii) Powder method?

3 M

3(b)(ii)
Calculate Bragg angle if (200) planes of a BCC crystal with lattice parameter 2.814Å give second order reflection with X-rays of wavelength 0.71Å.

4 M

4(a)
Calculate the critical radius ratio of an ionic crystal in ligancy 4 configuration.

5 M

4(b)
Determine the concentration of conduction electron in a sample of Silicon if one in every million Silicon atom is replaced by a Phosphorous atom. Assume every Phosphorous atom to be singly ionized. Si has a molar mass of 0.028 kg/mole and density of 2300 kg/m

^{3}/
5 M

4(c)
If a gas contains 1.2×10

^{27}atoms/m^{3}and radius of atom is 0.53Å, then calculate electronic polarizability and dielectric constant. Find the capacitance of a parallel plate capacitor having this gas inside, with plate area 1 cm^{2}and plate separation 0.12 cm.
5 M

5(a)
Find Miller Indices of a plane whose intercepts are a, 4a and a, where a is the lattice constant. Draw (102), (201] and (040) in a cubic unit cell.

5 M

5(b)
In a semiconductor with Hall co-efficient 145cc/C having width of 2 cm and thickness 0.2 cm with a magnetic field induction of 2T along the smaller dimensions, a current of 150mA is passing. Calculate the current density and Hall voltage.

5 M

5(c)
Write Sabine's formula explaining each term. Explain how this formula can be used for the determination of absorption co-efficient of a given material.

5 M

6(a)
Write five distinct differences between Frenkel and Schottky defect.

5 M

6(b)
Explain how a voltage difference is generated in a p- junction when it is used in a photovoltaic solar cell.

5 M

6(c)
Explain the principle, construction and working of a magnetostriction oscillator to produce ultrasonic waves.

5 M

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