Bangalore University 2005-2nd Sem B.E 1st/ -Engineering Physics-y/ - Question Paper

Page NoI. . 1    FHY12/22

USN

First/Second Semester B.E Degree Examination, July/August 2005

I

f    Common to all Branches

Engineering Physics

[Max. Marks : 100

Note: 1. Answer any FIVE full questions.

2.    All questions carry eqla marks.

3.    Answers mttst be specific and precise.

4- Draw neat sketches wherever necessary.

Electron mass m = 9.11 x 10^-31A:<7 Electron charge e =' 1.6 x 10^-19C Velocity of light c = 3 x 10^sm/s;

Plancks constant /i = 6.63 x 10^-34 J.S "" ¹    Perrriitivity of vacuum, e₀= 8.85 x 10^-12 F/M

.    Avagadros number, = 6.025x 10²⁶/Kmole

Boltzmann constant, K = 1.38 x 10^-23 J /K

1.    (a) What are matter waves ? Show that the electron accelerated by a potential

difference V volts is A = 1.226/Wnm for non- relativistic case.

(b)    Explain phase velocity and group velocity. Derive the expression for de Braglie wave length using the concept of group velocity.

(c)    The speed of electron is measured to within an uncertainty of 2.2 x 10*m/s in one dimension. What is the minimum width required by the electron to be confined in an atom.    (e+io+4 Marks)

2.    (a) What is a wave function ? Give its significance. Assuming a particle of mass

^-m is confined in a field free region between impenetrable walls at x 0 and

x = a, show that the stationary energy levels cf the particle are given by E_u n²A.²/8mar

(b) Explain the BCS theory of super conductity.

(cj A quantum particle confined to one-dimensional box of width a is known to be in its first excited state. What is the probability of the particle in central half?    (10+5+5 Mark*)

3.    (a) How does the electrical resistance of the metal change with impurity and

temperature?

(b)    Derive the expression for electrical conductivity in metals interms of relaxation time and explain any three draw backs of classical theory of free electrons.

(c)    Find the probability with which an energy level 0.2eV below fermilevel being occupied at room temperature of 300iT and lOOOif.    (5+10+5 Marks)

4.    (a) Explain the properties of Ferrites and mention its two uses.

(b) Explain with theory how static dielectric constant of a dielectric material is determined and explain its frequency dependance.

(c) The dielectric constant of He gas at NTP is 1.0000684. Calculate the electronic polarisability of He atoms if the gas contains 2.7 x 10²⁵ atoms per m³.

(5+10+5 Marks)

5.    (a) Explain the terms 'stimulated emission and population inversion. Obtain an

expression for energy density of photons in terms of Einsteins co-fficients.

(b)    Explain the construction and working of Ruby Laser

(c)    Write a note on measurement of pollutents in atmosphere using laser.

(10+6+4 Marks)

6.    (a) Explain the origin of characteristic X-rays.

(b)    Derive Braggs law.

(c)    Explain the principle of light propagation in an optical fibre. Derive the expression for numerical aperture in terms of refractive indices of core and cladding.

(d)    Calculate the number of modes that cafi be propagated inside an optical fibre, given n_CQTe - 1.53,    = 1-50, core radians 50fim, X = 1 fim.

n_Core = 1.53,    = 1.50, core radians 50(xm A = lfim    (s+5+6+4 Marks)

7.    (a) Explain the structure of NaCl and calculate the packing fraction for a bcc

structure.    -

(b)    Obtain the expression for inter planar distance interms of Miller indices.

(c)    Sketch the following planes in a cubic unit cell (101), (121 ),(010)

_r    (10+5+5 Marks)

8.    (a) Explain the term MEivIS. Discuss different materials used for MEWS.

(b)    Explain the advatages and disadvantages of composite materials.

(c)    Discuss the different types of nano scale systems.    (c+s+s Marks)

Attachment: bangalore-university-2005-b-e-19342-1.pdf

Earning:   Approval pending.