First/Second Semester B.E. Degree Examination, June 2014 Engineering Physics-Model question paper for VTU examination

USN 10PHY12/22

First/Second Semester B.E. Degree Examination, June 2014

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, m_e = 9.1×10^-31 kg,

k = 1.38×10^-23 J/K, ε₀ = 8.854×10^-12 F/m

PART-A

1 a. i) The law which describes the blackbody radiation completely is

A) Planck’s law B) Stefan’s law C) Wien’s law D) Rayleigh-Jean’s law

ii) Photoelectric effect establishes

A) wave nature of light B) particle nature of light C) dual nature of light D) None of these

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) If the group velocity of the de-Broglie waves associated with a particle is 3×10⁴ m/sec, the velocity of the particle is

A) 3×10⁸ m/s B) 3×10¹² m/s C) 3×10⁴ m/s D) None of these

b. Describe Davisson and Germer experiment for confirmation of de-Broglie hypothesis. (06marks)

c. What is Planck’s radiation law? Show how Wien’s law and Rayleigh-Jean’s law can be derived from it. (06 Marks)

d. Find the de-Broglie wavelength of particle of mass 0.65 MeV/C² has a kinetic energy 80 eV. (04 marks)

2 a. i) The probability of finding the particle within an element of volume dτ is

1. 0 B) ∫│ψ²│dτ C) ∫│ψ│dτ D) ∫│ψ^*│dτ

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) 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

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. State and explain Heisenberg’s uncertainty principle and prove that nuclei do not contain electron. (05 Marks)

d. A quantum particle confined to one dimensional box of width ‘a’ is in its first excited state. What is the probability of finding the particle over an interval of ( marked symmetrically at the centre of box. (05 Marks)

3 a. i) The fermi factor for E = E_F at T > 0K is

A) 1 B) ½ C) 0 D) 2

ii) Mobility of electron is

A) Reciprocal of conductivity B) Flow of electrons per unit

C) Reciprocal of resistivity D) Average electron drift velocity per unit electric field

iii) According to quantum free electron theory, the energy level in a metal are

A) Continuous B) Discrete C) Overlapping D) None

iv) For ordinary metals, resistivity versus temperature curve at T = 0K

A) has a positive intercept B) has a negative intercept

C) goes through the origin D) none of these (04 Marks)

b. Using the free electron theory, derive an expression for electrical conductivity in metals. (06 Marks)

c. Discuss the various drawbacks of classical free electron theory of metals. What are the assuptions made in Quantum theory to overcome the same? (06 Marks)

d. Calculate the probability of an electron occupying an energy level 0.02 eV above the Fermi level and 0.02 eV below the Fermi level at 200 K. (04 marks)

4 a. i) Electronic polarisation

A) Independent of temperature B) Increases with temperature

C) Decreases with temperature D) None of these

ii) Which of the following is a piezoelectric material?

A) lead B) mica C) iron D) quartz

iii) Above Curie temperature, ferromagnetic substance becomes

A) antiferromagnetic B) strongly ferromagnetic C) paramagnetic D) diamagnetic

iv) If two charges q are separated by a distance L, dipole moment of the system is

A) q/L B) L/q C) qL D) q/L² (04 Marks)

b. Derive the expression for internal field in solids. (06 Marks)

c. Derive Claussius-Mossoti equation. (06 Marks)

d. Sulphur is elemental solid dielectric whose dielectric constant is 3.4. Calculate electronic polarizability if its density is 2.07× 10³ kg/m³ and atomic weight is 32.07. (04 Marks)

PART-B

5 a. The pumping action in diode laser is by,

1. Optical pumping B) Electric discharge C) Reverse bias D) Forward bias

ii) The life time of an atom in a metastable state is of the order of

1. A few seconds B) unlimited time C) a nanosecond D) few milliseconds

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) The required condition to achieve laser action in a system is

A) state of population inversion B) existence of metastable state

C) a resonant cavity D) all the three

b. What is holography? Explain principle of hologram recording using laser. (05Marks)

c. Explain the construction and working of He-Ne laser, with the help of suitable diagrams.

(07 Marks)

d. The average output power of laser source emitting a laser beam of wavelength 633nm is 5 mW. Find the number of photons emitted per second by the laser source. (04 Marks)

6 a. i) According to Meissner effect, material in superconducting state is,

A) Paramagnetic B)diamagnetic C) ferromagnetic D) anti-ferromagnetic

ii) Attenuation in optic fiber is due to

A) absorption B) scattering C) radiation loss D) all the above

iii) The conductivity of a superconductor is

A) infinite B) Zero C) finite D) none of these

iv) In a single mode fiber, the diameter of the core is nearly equal to

A) 125 m B) 100 m C) 50 m D) 10 m (04 Marks)

b. Discuss BCS theory of superconductor. Explain SQUID. (07 Marks)

c. Describe the point to point communication system, with the help of block diagram (05 Marks)

d. The refractive indices of core and cladding are 1.50 and 1.48 respectively in an optical fiber. Find the numerical aperture and angle of acceptance. (04 Marks)

7 a. i) Packing factor of diamond crystal is

1. 34% B) 52% C) 68% D) 74%

ii) In Bragg’s spectrometer, for every rotation θ of the turn table, the detector turns by an angle,

A)θ B) 4θ C) 2θ D) θ/2

iii) The miller indices of the plane parallel to the x and y axes are

A) (100) B) (010) C) (001) D) (111)

iv) Which one of the following Bravais lattices is not found in cubic crystal?

A) Simple cubic B) Face centered C) Body centered D) Base centered (04 Marks)

b. Derive expression for interplanar spacing in terms of Miller indices (06 Marks)

c. Explain how Bragg’s spectrometer is used for determination of interplanar spacing in a crystal. (04Marks)

d. Calculate the glancing angle of the (110) plane of a simple cubic crystal (a=2.814Å) corresponding to second order diffraction maximum for the x-rays of wavelength 0.710 Å. (04 Marks)

8 a. i) The minimum size of the matter below which the properties become size dependent is called

A) Pico size B) Nano size C) Micro size D) Macro size

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) The elastic behavior of a liquid is characterized by its

A) Youngs modulus B) Modulus of rigidity C) Bulk modulus D) Poisson’s ratio

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. (06 Marks)

c. What is NDT? Describe the NDT method of detection of flaws in solid using ultrasound. (06Marks)

d. Explain two methods of preparation of Nanomaterials in brief. (04 Marks)