1(a) Outline Bohr’s theory of
hydrogen atom and derive an expression for the radius of the first Bohr orbit
for the normal hydrogen atom. (6 Marks)
(b) What are ionic crystals?
Explain the formation of an ionic crystal and obtain an expression for its
cohesive energy. (6 Marks)
(c) Calculate the potential
energy of the system of Na+ and Cl- ions when they are
0.2 nm apart. (4 Marks)
(d) The atomic weights and
densities of aluminium and copper are 26.98 and 63.54 and 2700 kg/m3
and 8960 kg/m3 respectively. Calculate the number of atoms present
in unit volume of aluminium and copper. (4 Marks)
2(a) Write a note on various
symmetry operations present in a crystal. (4 Marks)
(b) What are Miller indices?
Illustrate with examples. Draw (112) and (232) planes. (6 Marks)
(c) Explain with neat sketches
the different imperfections in a crystal. (6 Marks)
(d) The fraction of vacancy sites
in a metal is 10-10 at 5000C. What will be the fraction
of vacancy sires at 10000C.? (4 Marks)
3(a) Discuss a method of
investigating the structure of a single crystal using X-rays. (6 Marks)
(b) Write a note on relaxation
time. (4 marks)
(c) Explain quantum mechanical
tunneling in solids and its significance. (6 Marks)
(d) A copper wire whose diameter
is 0.16 cm carries a steady current of 10 amp. What is the current density in
the wire? Also calculate the drift velocity of the electrons in copper. (4
Marks)
4(a) Discuss salient features of
Debye’s theory of specific heat of solids. (4 Marks)
(b) Discuss the domain structure
in ferromagnetic materials. Explain the reasons for the strong ferromagnetic
property found in iron, cobalt and nickel. (6 Marks)
(c) Discuss Langevin’s theory for
a paramagnetic gas and obtain an expression for the paramagnetic susceptibility
of the gas. What are the main drawbacks of this theory? (6 Marks)
(d) Compute Debye temperature for
diamond whose atomic weight and Young’s modulus are 12 and 1012 Nm2
respectively. Density of diamond is 3500 kg/m3. (4 Marks)
5(a) Derive the London equations
and explain the term coherent length. Explain 1-2-3 superconductors. (6 Marks)
(b) Discuss d.c and a.c Josephson
effect and explain their importance. (6 Marks)
(c) Explain the properties of
Cooper pairs. (4 Marks)
(d) The London penetration depths
for Pb at 3K and 7.1K are respectively 39.6nm and 173 nm. Calculate its
transition temperature as well penetration depth at 0K. (4 Marks)
6(a) Distinguish between Zener
breakdown and avalanche breakdown. (4 Marks)
(b) Derive an expression for the
density of holes in an intrinsic semiconductor. Suggest a method for evaluating
the energy gap of the semiconductor. (6 Maks)
(c) Discuss the physical origin
and uses of Hall effect. (6 Marks)
(d) The room temperature electron
mobility in GaAs is 0.08 m2V-1S-1. Calculate
the diffusion constant of electrons. (4 Marks)
7(a) What is meant by dielectric
loss? State its importance. (4 Marks)
(b) How does dielectric constant
of a solid containing permanent dipole vary with temperature? Illustrate your
answer with an example. (6 Marks)
(c) Discuss the salient features
of optical absorption in the case of metals, semiconductors and insulators. (6
Marks)
(d) A fiber optic link is
operated at a wavelength of 1.3 mm.
Find the maximum bit-rate of a 25 km line made from a multimodal step-index
fiber. Given n1=1.46 and n2=1.46. (4 Marks)
8(a) Write notes on gaseous
insulating materials and liquid insulating materials. (6 Marks)
(b) Differentiate between
thermosetting resins and thermoplastic resins. (6 Marks)
(c) Write a note on laminated
composites. (4 Marks)
(d) Calculate the Young’s modulus
of a composite with glass fibers reinforced in phenol formaldehyde plastics.
The volume fraction of plastics is 33.3%. The modulus of glass fiber is 6.9×104
MPa and that of polymers 6.9×102 MPa. (4 Marks)
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