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## Wednesday, March 6, 2013

### First/Second Semester B.E. Degree Examination, June 2013 Engineering Physics-Model question paper

USN                                                                     10PHY12/22

First/Second Semester B.E. Degree Examination, June 2013
Engineering Physics
Time: 3 hrs.                                                                                                                 Max. Marks:100

Note: 1. Answer any FIVE full questions, choosing atleast two from each part.
2. Answer all objective type questions only in OMR sheet page 5 of the answer booklet.
3. Answer to objective type questions on sheets other than OMR will not be valued.
4. Physical constants: h = 6.626×10-34 Js, c = 3×108 m/s, me = 9.1×10-31 kg,
k = 1.38×10-23 J/K, ε0 = 8.854×10-12 F/m

PART-A
1 a.  i) Ke,Kp and Ka are respective energy of an e-, a proton and aparticle of same de-Broglie wavelength. Then,
A) Ke>Kp>Ka          B) Ke>Kpa         C) Kep
a         D) Ke=Kp= Ka
ii) Recoil electron in Compton scattering carry maximum kinetic energy when x-ray scattering angle θ =
A) 1800                         B) 00                            C) 900                            D) 650
ii) Experimental evidence for the existence of matter waves was first provided by
A) de-Broglie     B) Davisson and Germer           C) G.P.Thomson                D) Max Planck
iv) Green light incident on a surface releases photoelectrons from the surface. If now blue light is incident on the same surface, the velocity of electrons
A) increases          B) decreases            C) remains same          D) becomes zero         (04 marks)
b. Show that group velocity is equal to particle velocity.    (05marks)
c. What is Planck’s radiation law?  Show how Wien’s law and Rayleigh-Jean’s law can be          derived from it. (07 Marks)
d. An electron beam has a de-Broglie wavelength of 2 ×10-12 m. Find the kinetic energy, phase and group velocities of de-Broglie waves.           (04 marks)
2 a. i) If free electron exists in a nucleus, its energy value must have a minimum energy of about
A) 4 MeV        B) 9.9 MeV                              C) 9.9 KeV              D) 4 KeV
ii) The product of uncertainty between angular momentum and angular displacement is
A) ≥ ħ/2p        B) ≥ ħ /4p                                 C) ≤ ħ /4p                 D) ≥ ħ /2
iii) If E1 is the energy of the lowest state of a one dimensional potential box of length ‘a’ and E2 is the energy of the lowest state when the length of the box is halved, then
A) E2 = E1                  B) E2 = 2E2                 C) E2 = E1/2                        D) E2 = 4E1
iv) The wavefunction is acceptable if it is
A) Finite everywhere                                           B) Continuous everywhere
C) Single valued everywhere                               D) All of these
(04 Marks)
b. Solve the Schrödinger’s wave equation for allowed energy values in case of a particle in a potential box.                                                                                                                                 (06 Marks)
c. What is a wave function? Explain the properties of a wave function.                               (04 Marks)
d. An electron is bound in one dimensional potential well of width 0.18 nm. Find the energy value in eV of the second excited state.                                                                                       (04 Marks)
3 a. i) The classical value of molar specific heat of a conductor is
A) 3/2 R            B) ½ R                        C) 3R              D) 5/2 R
ii) The Fermi energy of a metal at absolute zero temperature is proportional to
A) n1/3              B) n3/2              C) n2/3              D) n2
iii) According to quantum free electron theory, the energy level in a metal are
A) Continuous     B) Discrete      C) Overlapping           D) None
iv) Which one of the following is correct for current density?
A) J = neAvd   B) J = neA/vd C) J = nevd     D) J = 1/nevd
(04 Marks)
b. Define relaxation time and discuss the dependence of electrical resistivity of metals with temperature and impurity.                                                                                                          (06 Marks)
c. What is Fermi energy? Discuss variation of Fermi factor with energy and temperature.   (06 marks)
d. A uniform silver wire has resistivity 1.54×10-8 ohm-m at room temperature for an electric field 2 v/m.  Calculate relaxation time and drift velocity of the electrons, assuming that there are 5.8×1022 conduction electrons per cm3 of the material.                                                                            (04 marks)
4 a. i) Orientation polarization occurs
A) In all dielectrics     B) in polar dielectrics        C) in non-polar dielectrics
D) in ionic dielectrics
ii) Ultrasonic waves can be produced by
A) Photoelectric effect method                B) Inverse piezoelectric effect method
C) Dielectric heating method                    D) High energy ball milling method
iii) The susceptibility of a diamagnetic material is
A) Infinity             B) positive       C) zero                        D) negative
iv) In a magnetic material, the major contributor to magnetism is
A) orbital motion of electrons                    B) nuclear spin
C) spin motion of electrons                        D) none of these                                             (04 Marks)
b. Derive the expression for internal field in solids.                                       (08 Marks)
c. What are soft magnetic materials? Discuss their properties.                                               (04 Marks)
d. If NaCl crystal is subjected to an electric field of 1000 V/m and the resulting polarization is 4.3×10-8 c/m2, calculate the static dielectric constant of NaCl.                                 (04 Marks)

PART-B
5 a. i) In semiconductor laser, the material used is
A) any semiconductor                         B) direct band gap semiconductor
C) indirect band gap semiconductor   D) not a semiconductor
ii) The number of modes of standing waves in the resonant cavity of length 1m, if He-Ne laser operating at wavelength 6328 Å is
A) 3.16 × 106                   B) 3.16 × 1010              C) 3.16 × 108           D) None of these
iii) Emission of a photon by an excited atom due to interaction of external energy is called
A) Spontaneous emission   B) Stimulated emission        C) Induced absorption
D) Light amplification
iv) 3D image of an object constructed by hologram is the process of
A) Intensity recording                                    B) Phase information recording
C) Both phase and intensity information recording   (04 Marks)
b. Write a note on measurement of pollutants in atmosphere using laser.                              (06Marks)
c. Explain the construction and working of He-Ne laser, with the help of suitable diagrams.
(05 Marks)
d. The ratio of population of two energy levels is 1.059×10-30. Find the wavelength of light emitted at 300K.       (04 Marks)
6 a. i) Graded index fiber can be
A) single mode fiber only           B) multimode fiber only
C) both single mode and multimode D) depends on the surrounding medium
ii) The loss of power by the optical signal through the optical fiber is mainly due to
A)    Rayleigh scattering  B) Raman scattering  C) Wien’s scattering
D) All of these
iii) When the type-I superconducting material is placed in an external magnetic field, it
A) attracts the magnetic lines  B) enhances the magnetic flux lines
C) repels the magnetic flux lines
D) does not influence magnetic field of lines
iv) Superconductors are
A)    Diamagnetic B) paramagnetic C) ferromagnetic D) antiferromagnetic          (04 Marks)
b. Discuss BCS theory of superconductor. Explain SQUID.                                                 (07 Marks)
c. Derive the expression for numerical aperture of an optical fiber.               (05 Marks)
d. The angle of acceptance of an optical fiber is 300 when kept in air. Find the angle of acceptance when it is in a medium of refractive index 1.33.                   (04 Marks)
7 a. i) Four types of Bravais lattices are observed in
A) Rhomohedral system                      B) Orthorhombic system
C) Triclinic system                  D) Monoclinic system
ii) A plane intercepts at a, b/2, 2c in a simple cubic unit cell. The miller indices of the plane are
A) (214)      B) (241)      C) (421)           D) (124)
iii) The coordination number for a face centered cubic lattice is
A) 12                  B) 8                 C) 6                 D) 26
iv) For every rotation by angle q in Bragg’s spectrometer, detector turns by an angle
A) q                 B)3q                C) 4q               D) 2q                           (04 Marks)
b. Define unit cell and primitive cell. Describe crystal structure of diamond.           (08 Marks)
c. Derive Bragg’s law for X-ray diffraction.                                                                          (04Marks)
d. Calculate the glancing angle for incidence of X-rays of wavelength 0.58Å on the plane (132) of NaCl which results in second order diffraction maxima taking the lattice as 3.81Å.                    (04 Marks)
8 a. i) In a carbon nanotube, the bond between the carbon atoms is
A) Metallic      B) ionic           C) covalent      D) hydrogen
ii) A constant testing of product without causing any damage is called
A) minute testing   B) destructive testing    C) non-destructive testing    D) random testing
iii) Ultrasonic waves can exist only as longitudinal waves in
A) Solid          B) Liquid        C) Gases          D) All the above
iv) The state of matter around the nanosize is known as
A) Liquid state            B) Plasma state
C) Mesoscopic state    D) Solid state                                                                                      (04 Marks)
b. Explain density of states for various quantum structures.                                                  (08 Marks)
c. Describe a method of measuring velocity of ultrasonic waves in liquid. (08 Marks)