Bangalore University 2011-1st Sem B.Sc PMCS (Physics, Mathematics, Computer Science) Vester , (semester scheme) PHYSICS(-VII) - Question Paper

Time : three Hour Max. Marks:60

PART-A
I. ans any 5 of the subsequent. (5x6=30)

1) Mentioning the postulates,derive Fermi-Dirac expression for the probability
distribution of particles. (MARKS 6)

2) How is electrical conductivity related to the relaxation time? Establish the
relation ranging from them. (MARKS 6)

3) a) discuss the terms :
i) phase space ii)phase point
b) describe Fermi energy.
c) Mention 2 properties of nanomaterials. (MARKS 2+2+2)

4) Write a note on continuous and characteristic X-ray spectra. (MARKS 6)

5) discuss the powder method of X-ray diffraction with necessary theory. (MARKS 6)

6) Distinguish ranging from conductors,semiconductors and insulators based on band
theory of solids. (MARKS 6)

7) Derive an expression for carrier concentration in an intrinsic semiconductor on the
basis of Fermi-Dirac statistics. (MARKS 6)

8) a) What is Meissner effect?
b) show that magnetic susceptibility of a superconductors is -1.
c) Write a note on superconductors magnets. (MARKS 1+3+2)


PART-B
II. ans any 4 of the subsequent : (4x5=20)

9) 5 bosons are distributed in 2 compartments. The first is having three
cells and second 4. obtain the thermodynamic probability for the macro state,
i)(5,0) ii)(4,2).

10) The atomic radius for sodium is 1.66x10-10 m.Calculate its Fermi energy at
absolute zero.

11) In Compton effect, the wavelength of x-ray radiation scattered at an
angle of 45o is 0.022x10-10m.Calculate the wavelength of incident x-ray.

12) A crystal plane cuts crystallographic axes at 2a,2b,c/3 respectively. What
are the miller indices of the plane ?

13) compute the drift velocity of the electrons in a Cu plate when a current
of 250 A is flowing across the faces of it. The area of the plate is
1.5x10-4 m2 and the density of free electron in Cu is 8.8x1028 m3.

14) compute the Hall voltage developed in Ge crystal of thickness 0.5x10-3 m.
when a magnetic field of 0.7 T is applied. The current density is 250 Am-2
and the electron density is 2x1023 m-3.



PART-C
III. ans any 5 of the subsequent : (5x2=10)

a) provide major difference ranging from Bosons and Fermions.

b) Visible light cannot be used for crystal diffraction. discuss.

c) All the electrons do not contribute to the specific heat of metals. Why?

d) Why is Hall coefficient of semiconductor positive?

e) Electromagnets on cooling are called superconducting magnets. discuss.

f) Why are p-type and n-type materials electrically neutral?

Earning:   Approval pending.