Engineering Physics - Jun 2013

First Year Engineering (P Cycle) (Semester 1)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks.

Choose the correct answer for the following :-

1 (a) (i) If red and blue stars emits radiator of continuous wavelength, then according to Wien's displacement law,
(A) Blue star is hotter than red star
(B) Red star is hotter than blue star
(C) Both stars are at same temperature
(D) Difficult to conclude.(1 marks) 1 (a) (ii) The expression for de-Broglie wavelenght for an electron under an accelerating potential V is,
$$ (A) \ \dfrac {12.26}{\sqrt{V}}m \$$B) \ \dfrac {12.26}{\sqrt{V}}A^{\circ} \$$C) \ \dfrac {12.26}{\sqrt{V}}nm \$$D) \ \dfrac {12.26}{\sqrt{V}}\mu m\\$$\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt1 (a) (iii)\lt/b\gt A particle moves with velocity 3×10\ltsup\gt6\lt/sup\gt ms. The wavelength associated with it is 1 nm. Then group velocity of the particle is, \ltbr\gt (A) 3×10\ltsup\gt8\lt/sup\gt mS\ltsup\gt-1\lt/sup\gt \ltbr\gt (B) 3×10\ltsup\gt10\lt/sup\gt mS\ltsup\gt-1\lt/sup\gt \ltbr\gt (C) 3×10\ltsup\gt6\lt/sup\gt mS\ltsup\gt-1\lt/sup\gt \ltbr\gt (D) 1.5 ×10\ltsup\gt6\lt/sup\gt mS\ltsup\gt-1\lt/sup\gt\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt1 (a) (iv)\lt/b\gt According to the Compton effect. The wavelength of X-rays scattered at an angle greater than zero. \ltbr\gt (A) Decreases \ltbr\gt (B) Doesn't change \ltbr\gt (C) Increases \ltbr\gt (D) None of these\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt1 (b)\lt/b\gt Derive an expression for group velocity on the basic of superposition of waves. Also obtain the relation between group velocity and phase velocity.\lt/span\gt\ltspan class='paper-ques-marks'\gt(8 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt1 (c) \lt/b\gt Show that Planck's law reduces to Wien's law and Rayleigh-Jeans law under certain conditons.\lt/span\gt\ltspan class='paper-ques-marks'\gt(5 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt1 (d) \lt/b\gt Calculate the de-Broglie wavelength associated with an electron of energy 1.5 eV.\lt/span\gt\ltspan class='paper-ques-marks'\gt(3 marks)\lt/span\gt \lt/span\gt -------------- \ltspan class='paper-comments'\gt ### Choose the correct answer for the following :- \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt2 (a) (i)\lt/b\gt The energy of the lowest state in one dimensional potential box of length a-1 unit is, \ltbr\gt $$ (A) \ \dfrac {h^2}{8m} \$$B) \ zero \$$C) \ \dfrac {h^2}{4ma^2}\$$D) \ \dfrac {h^2}{2ma^2}\$$(1 marks) 2 (a) (ii) For a particle which is not bound to any system and is free, the energy eigen value is,
(A) zero
(B) finite but not quantized
(C) infinity
(D) finite but quantized(1 marks) 2 (a) (iii) If the uncertainly in the position of a particle is equal to its de-Broglie wavelenght then
$$ (A) \ \Delta P \ge \dfrac {h}{4\pi}\$$B) \ \Delta P > \dfrac {h}{2\pi}\$$C) \ \Delta P > \dfrac {P}{4\pi}\$$D) \ \Delta P \ge \dfrac {h}{P}\\$$\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt2 (a) (iv)\lt/b\gt For an electron to be present inside the nucleus of an atom the uncertainly in the position of the electron must be, \ltbr\gt (A) more than or equal to the radius of the nucleus \ltbr\gt (B) more than or equal to the diameter of the nucieus \ltbr\gt (C) more than the diameter of the nucieus \ltbr\gt (D) less than or equal to the diameter of the nucleus.\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt2 (b)\lt/b\gt Using time independent Schrodinger's wave equation, obtain the expression for the normalized wave function for a particle in one dimensional potential well of infinite height.\lt/span\gt\ltspan class='paper-ques-marks'\gt(8 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt2 (c) \lt/b\gt State Heisenberg's uncertainly principle. Write its physical significance.\lt/span\gt\ltspan class='paper-ques-marks'\gt(4 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt2 (d) \lt/b\gt A spectral line of wavelenght 5461 A has a width of 10\ltsup\gt-4\lt/sup\gt A. Evaluate the minimum time spent by the electrons in the upper energy state.\lt/span\gt\ltspan class='paper-ques-marks'\gt(4 marks)\lt/span\gt \lt/span\gt -------------- \ltspan class='paper-comments'\gt ### Choose the correct answer for the following :- \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt3 (a) (i)\lt/b\gt In the following the ohm's law is, \ltbr\gt $$ (A) \ J=\sigma E \$$B) \ J=\dfrac {\sigma}{E}\$$C) \ J=\sigma E^2 \$$D) \ J=\dfrac {E}{\sigma}\$$ (1 marks) 3 (a) (ii) Mobility of electron is,
(A) Reciprocal of conductivity
(B) Average electrons drift velocity per unit electric field
(C) Flow of electrons per unit cross sectional area
(D) Reciprocal of resistivity(1 marks) 3 (a) (iii) The dependence of mean free path λ on temperature T is
$$ (A) \ \lambda \alpha T $$
$$ (B) \ \lambda \alpha \sqrt{T} $$
$$ (C) \ \lambda \alpha \dfrac {1}{T} $$
$$ (D) \ \lambda \alpha \dfrac {1}{\sqrt{T}} $$ (1 marks) 3 (a) (iv) According to free electron theory, the free electrons are treated as,
(A) Rigidity fixed lattice points
(B) Liquid molecules
(C) Gas molecule
(D) None of these(1 marks) 3 (b) Define Fermi energy and Fermi factor. Discuss the variation of fermifactor with temperature and energy.(8 marks) 3 (c) What is mean collision time? Using free electron theory in a metal, obtain an expression for electrical conductivity in terms of mean collision time.(6 marks) 3 (d) State and explain Matthiessen's rule.(2 marks)

Choose the correct answer for the following :-

4 (a) (i) Electronic polarization,
(A) Independent of temperature
(B) Increases with temperature
(C) Decreases with temperature
(D) None of these(1 marks) 4 (a) (ii) The correct relation among the following 4 equations is,
(A) E=ε₀(ε_r-1)P
(B) P=ε₀(ε_r-1)E
(C) ε_r=χ-1
(D) D=ε₀(ε_r-1)E (1 marks) 4 (a) (iii) For Ferromagnetic substances, the Curie-Wiess law is given as,
$$ (A) \ \epsilon_r = \dfrac {C}{T} \$$B) \ \epsilon_r= \dfrac {T-0}{C} \$$C) \ \epsilon_r= \dfrac {C}{(T-0)}\$$D) \ \epsilon_r=\dfrac {C}{(T+0)}\\$$\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt4 (a) (iv)\lt/b\gt In the inverse piezoelectric effect, \ltbr\gt (A) Ultrasonic waves are produced \ltbr\gt (B) Electromagnetic waves are produced \ltbr\gt (C) Microwaves are produced \ltbr\gt (D) None of these\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt4 (b)\lt/b\gt What is internal field? Derive an expression for internal field in case of one dimensional array of atoms in dielectric solids.\lt/span\gt\ltspan class='paper-ques-marks'\gt(8 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt4 (c) \lt/b\gt Describe magnetic hysteresis in Ferromagnetic materia.\lt/span\gt\ltspan class='paper-ques-marks'\gt(5 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt4 (d) \lt/b\gt Explain any three application of piezoelectric material.\lt/span\gt\ltspan class='paper-ques-marks'\gt(3 marks)\lt/span\gt \lt/span\gt -------------- \ltspan class='paper-comments'\gt ### Choose the correct answer for the following :- \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt5 (a) (i)\lt/b\gt The pumping action in diode laser is by, \ltbr\gt (A) Optical pumping \ltbr\gt (B) Electrical discharge \ltbr\gt (C) Reverse bias \ltbr\gt (D) Forward bias\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt5 (a) (ii)\lt/b\gt The expression for energy density in terms of Einstein's coefficients, \ltbr\gt $$ (A) \ U_{\gamma}= \dfrac {B}{A} \left [ \dfrac {1}{e^{h\gamma /KT}-1} \right ]\$$B) \ U_{\gamma}=\dfrac {A}{B} \left [ \dfrac {1}{1-e^{h\gamma / KT}} \right ]\$$C) \ U_{\gamma}=\dfrac {A}{B} \left [ \dfrac {1}{e^{h \gamma / KT}-1} \right ] \$$D) \ U_{\gamma}=\dfrac {A}{B} \left [ e^{h\gamma / KT }-1 \right ] \$$ (1 marks) 5 (a) (iii) In order to see the image of an object recorded by holography,
(A) it is enough if we just have the hologram.
(B) we need the hologram and the reference beam.
(C) we need the hologram, the reference beam and the object beam.
(D) we need the hologram, the reference beam and the object beam as well as the object.(1 marks) 5 (a) (iv) In a laser system when the energy difference between two energy levels is 2× 10^-19 J, the average power output of laser beam is found to be 4 mw. Then number of photons emitted per second is.
(A) 2×10¹⁶
(B) 2× 10^-16
(C) 0.5×10¹⁶
(D) 2×10¹⁹(1 marks) 5 (b) Describe the construction of He-Ne laser and explain its working, with the help of energy level diagram and metion few applications.(8 marks) 5 (c) Explain the terms spontaneous emission and stimulated emission.(4 marks) 5 (d) Explain laser welding and cutting process with diagrams.(4 marks)

Choose the correct answer for the following :-

6 (a) (i) Superconductor arc
(A) Ferromagnetic
(B) Paramagnetic
(C) Antiferromagnetic
(D) Diamagnetic(1 marks) 6 (a) (ii) All high temperature superconductors are different types of oxides of,
(A) Mercury,
(B) Lead
(C) Copper
(D) Tin (1 marks) 6 (a) (iii) The quantum of magnetic flux is given by,
$$ (A) \ \dfrac {2e}{h}\$$B) \ \dfrac {h}{2e}\$$C) \ \dfrac {he}{2} \$$D) \ \dfrac {2h}{e}\\$$\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt6 (a) (iv)\lt/b\gt Numerical aperture of an optical fibre depends on \ltbr\gt (A) Acceptance angle \ltbr\gt (B) Diameter of the fibre \ltbr\gt (C) Critical angle \ltbr\gt (D) None of these\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt6 (b)\lt/b\gt Discuss point to point optical fibre communication system and mention its advantages over the conventional communication systems.\lt/span\gt\ltspan class='paper-ques-marks'\gt(6 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt6 (c) \lt/b\gt Define superconductivity and explain Type I and Type II supercondutors.\lt/span\gt\ltspan class='paper-ques-marks'\gt(6 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt6 (d) \lt/b\gt The angle of acceptance of an optical fibre is 30° when kept in air. Find the angle of acceptance when it is in a medium of refractive index 1.33\lt/span\gt\ltspan class='paper-ques-marks'\gt(4 marks)\lt/span\gt \lt/span\gt -------------- \ltspan class='paper-comments'\gt ### Choose the correct answer for the following :- \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt7 (a) (i)\lt/b\gt A crystal of hexagonal lattice has unit cell with sides, \ltbr\gt (A) a ≠ b ≠ c, α = β = 90°, γ=120° \ltbr\gt (B) a = b = c, α = β = 90°, γ=120° \ltbr\gt (C) a ≠ b = c, α = β = γ=90° \ltbr\gt (D) a = b ≠ c, α = β = 90°, γ=120°\lt/span\gt\ltspan class='paper-ques-marks'\gt(1 marks)\lt/span\gt \lt/span\gt\ltspan class='paper-question'\gt\ltspan class='paper-ques-desc'\gt\ltb\gt7 (a) (ii)\lt/b\gt In Bragg's spectrometer, for every rotation ? of the turn table, the detector turns by an angle. \ltbr\gt $$(A)\ \theta \ (B)\ 4\theta \ (C)\ 2\theta \ (D)\ \dfrac{\theta}{2} $$(1 marks) 7 (a) (iii) The interatomic distance between the sodium and chlorine atoms in sodium crystal is
(A) 5.68 Å
(B) 2.81 Å
(C) 6.62 Å
(D) 5.51 Å(1 marks) 7 (a) (iv) The interplanar spacing in a crystal is Å and the glancing angle is 35°. For the first order Bragg reflection to take place, the wavelength of X-rays is,
(A) 1.147 Å
(B) 0.573 Å
(C) 1.638 Å
(D) 0.819 Å(1 marks) 7 (b) What are Miller indices? Explain the procedure to Miller indices with an example.(5 marks) 7 (c) Obtain the expression for interplanar spacing of 'a' for a cubic lattice.(5 marks) 7 (d) Calcualte the atomic packing factor for SC. FCC and BCC lattice.(6 marks)

Choose the correct answer for the following :-

8 (a) (i) An acoustic grating can be made by,
(A) Drawing lines on a glass plate
(B) Subjecting an optical grating to pressure waves of ultrasonic frequency
(C) It is only theoretical concept
(D) Setting up a standing waves pattern in a liquid using ultrasonic(1 marks) 8 (a) (ii) The velocity of ultrasonic wave through the liquid increases as,
(A) Bulk modulus decreases
(B) Density decreases
(C) Bulk modulus increases
(D) Volume increases(1 marks) 8 (a) (iii) The minimum size of matter below which the properties becomes size dependent is called,
(A) Pico size
(B) Nano size
(C) Micro size
(D) Macro size(1 marks) 8 (a) (iv) The number of carbon atoms present in C₆₀ molecule is
(A) 60
(B) 32
(C) 20
(D) 12(1 marks) 8 (b) Describe with simple illustrations, the two methods of preperation of nano material.(6 marks) 8 (c) Describe a method of measuring velocity of ultrasonic waves in solids. Using this how you can find the refidity modulus of the solid.(6 marks) 8 (d) Explain quantum structures.(4 marks)