Attempt any five from the following:

1 (a)
Draw the following in a cubic unit cell (0 1 2), (1 2 3), [1 2 1]

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1 (b)
Define the term space lattice, unit cell and lattice parameter.

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1 (c)
Determine the lattice constant for FCC lead crystal of radius 1.746 Å and also find the spacing of (2 2 0) plane.

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

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

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1 (f)
Why soft magnetic materials are used in core of transformers?

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1 (g)
Calculate the electronic polarizability of A

_{1}. Given number of Air atoms at NTP=2.7×10^{25}/m^{3}and dielectric constant of Ar=1.0024.
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2 (a)
Show that for intrinsic semiconductors the Fermin level lies midway between the conduction band and the valence band. Draw the energy level diagram a function of temperature for n-type of semi-conductor.

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2 (b)
Cu has FCC structure. If the interplanar spacing d is 2.08 A° for the set of (111) planes. Find the density and diameter of Cu atom. Give atomic weight of Cu is 63.54.

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3 (a)
What is hysteresis? Draw a hysteresis loop for ferromagnetic material and explain the various important points on it. For a transformer which kind of material will you prefer-the one with small hysteresis area or the big one?

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3 (b)
Derive Bragg's law. X-ray of unknown wavelength give first order Bragg's reflection at glancing angle of 20° with (2 1 2) planes of cooper having FCC structure. Find the wavelength of X-rays, if the lattice constant for cooper is 3.615 A°.

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4 (a)
Discuss Diamond structure with neat diagram and also determine the effective number of atoms / unit cell, co-ordination number and atomic radius in tems of lattice constant.

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4 (b)
Classify solids on the basis of energy band diagram.

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4 (c)
Explain orientational polarization with suitable diagram and write the mathematical expression of orientational polarizability.

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5 (a)
Calculate the number of atoms per unit cell of a metal having the lattice parameter 2.9 A° and density 7.87 gm/cm

^{3}. Atomic weight of metal is 55.85. Avogadro number is 6.023×10^{23}/gm mole.
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5 (b)
What is Hall effect? Mention its significance. How mobility can be determined by using Hall effect?

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5 (c)
The reverberation time is found to be 1.5 second, for an empty Hall and it is found to be 1.0 second when a curtain cloth of 20m

^{2}is suspended at the centre of the Hall. If the dimensions of the hall are 10×8×6m^{3}, calculate the coefficient of absorption of curtain cloth.
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6 (a)
Describe principle, construction and working of magnetostriction oscillator to produce ultrasonic waves.

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6 (b)
Briefly explain the different types of point defects.

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

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