Visvesvaraya Technological University (VTU) 2006 B.E FIRST SEMESTER , ENGINEERING PHYSICS - Question Paper

FIRST SEMESTER B.E. DEGREE EXAMINATION, JANUARY 2006
COMMON TO ALL BRANCHES
ENGINEERING PHYSICS
Time: three hrs. Max. Marks:100
Note: ans any 5 questions,
Electron mass m = 9.11*10 31
kg.
Electron charge e = 1.6*10 19
C
Velocity of light C = 3*10 five m/s.
Planck’s constant h = 6.63*10 34
Js
Permittivity of Vacuum e0 = 8.85 * 10 12
F/M
Avagadro’s number, NA = 6.025 * 10 26 /K mole
Boltzmann constant, k = 1.38*10 23
J/K
1. (a) discuss the duality of matter waves. (5 marks)
(b) define division – Germer experiment to establish the wave nature of electrons.
(10 marks)
(c) Compare the energy of a phoion with that of an electron when both are
associated with wave length of 0.2nm. (5 marks)
2. (a) Setup the Schrodiner’s wave formula and explain the case of a free particle.
(8marks)
(b) Distinguish ranging from kinds I and kind II superconductors. discuss briefly the
working of SQUID. (7 marks)
(c) An electron is bound in 1 dimensional infinite well of width one * 10 10
m. obtain
the energy values in the ground stage and 1st 2 excited states. (5 marks)
3. (a) discuss the terms drift velocity relaxation time and mean free path for free
electron. (5 marks)
(b) discuss density of states. Derive an expression for number of allowed states per
unit quantity of a solid
(c) compute the Fermi energy in eV for a metal at 0 K, provided that its density is
10500kg/m three . Atomic wt. is 107.9 and it has only 1 conduction electron per
atom. (5 marks)
4. (a) Distinguish ranging from hard and soft magnetic materials (5 marks)
(b) elaborate dielectrics? Derive an expression for internal field for 1 dimensional
array of dielectric solid. (10 marks)
(c) What should be the voltage needed to introduce a material of dielectric constants
ranging from the plates of a parallel plate capacitor of area 100mm two having plates
separation of 5mm and a charge of 3*10 C? Also, determine the applied electric
field (5 marks)
5. (a) With a neat sketch tag the requisites of a typical laser system. discuss why twolevel
energy system is not feasible to find laser action at thermal equilibrium?
(5 marks)
(b) Write the features of the Ruby and HeNe
systems with respect to the subsequent
(i) Active medium (ii) Energy level diagram, (iii) Laser Cavity
(iv) Operating wavelengths and (v) Applications. (10 marks)
(c) With a neat diagram tag themodes of propagation in an optical fiber.
compute the numerical aperture, relative refractive index difference. Vnumber
and number of modes in an optical fiber of core diameter 50mm, Core and
cladding refractive indices 1.41 and 1.40, at wave length 820 nm. (5 marks)
6. (a) discuss (i) Bravais lattices (ii) Lattice parameters, and (iii) difference
ranging from unit cell and primitive cell (6 marks)
(b) discuss the formula governing the diffraction of xrays.
obtain the miller indices
of a plane making kthe intercepts. 2a, 3b and 6c respectively on [100], [010] and
[001] directions. a, b and c rep0resent basis vectors. (5 marks)
(c) Derive an expression for inter planar spacing in a cubic system. define with
a neat diagram the structure of Nacl.
7. (a) elaborate composites? discuss. explain their merits in the situation of modern
application. A ruby laser emits IJ pulses of light whose wave lengths are 694nm.
What is the minimum number of CR three + ions in the ruby? (10 marks)
(b) Write a note on nanotechnology and its importance. (5 marks)
(c) What is a quantum bit? discuss (5 marks)
8. (a) With neat diagrams discuss the terms: (i) Acceptance angle and (ii) Numerical
aperture. find an expression for numerical aperture in terms of refractive indices
of core and cladding of an optical giver. Mention the factors contributing to the
fiber losses. (10 marks)
(b) What is attenuation in optical fiber? obtain the attenuation in an optical fiber of
length 500m, when the light signal of power 100 mw emerges out of the fiber
with 90mw. (5 marks)
(c) In a material at 300 K, 2 energy levels have a wavelength separation of one mn.
Calculate.
(i) The ratio of upper to lower level occupation densities when the material is in
thermal equilibrium. (5 marks)
(ii) The effective temperature when the levels are equally populated.

Earning:   Approval pending.