Engineering Physics Jan 2014

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First/Second Semester B.E. Degree Examination, Dec.2013 lJan.20l4

Engineering Physics

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Note: 1. Answer any FIW full questions, choosing at least twofrom each part.2. Answer all objective type questions only in OMR sheet page 5 of the ansipei booklet.3. Answer to objective fi;pe questions on sheets other than OMR will not:he.valued.4. Physic.u,l constants : h : 6.62 x 1tr34 JS, c : 3 x 108 m/s, m" : 9r,1"''*'1A31 kg.

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PART _ AI a. Choose the correct answers for the following : (04 Marks)

i) Photo electric effect signifiesA) particularc,aat:re of radiationB) wave natureofradiation

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C) both particulate and wave nature of radiationD) none of these 1",,,

ii) In a blackbody radiation spectrum, Wien's displacement law is true forA) high frequency region B) low &equency region

C) for all range of,,freQuencies D) none oftheseb. Explain with a neat,,diagram, how the Davison-Germer experiment proves the concept of

matter waves. (07 Marks)c. Obtain an expression for group velocity. (05 Marks)d. Calculate tho:de-Broglie wavelength associated with rain drops.:fi+ting under gravity with a

speed otoi;$,b "/s.

Given, the average diameter of the drops is t rnm a""a density of water is1000 kg/t'n' (04 Marks)

2 a. Choose the correct answers for the following :

. i) The uncertainty in location of a particle is equal' uncertainty in velocity if AxAp : h is

A)V u); c) 2v

ii) Uncertainty principle applies only between /6Y l\-q\,A) position and momentum B) energy and time ,'.'fl .enstou\ \f;ijC) any two canonically conjugate variables D) either A or B. \.{ t.rsnefrv / I /iii) If width of the potential well increases by 4 times, energy of the particle\r\ /"VilIt width of the potential well increases by 4 times, energy of the particle\r#.\ ,/^pt',A) reduces to 114 times B) reduces to 1116 times \o"V'C'7C) increases by 4 times D) increases by 16 times 'Y942

ir) Probability of finding the particle isA) highest in ground state B) lowest in first excited stateC) independent of energy of the state D) increases with energy of the state

C) all range of fiequencies ;,.",,,.- ,' D) not applicable for blackbody radiationiii) If the velocity of a particle douli&s, then de-Broglie wavelength

A) increases by 2 times . "ii, 1 B) decreasesby 2times

C) no change D) none of theseiv) Compton effect takes place

A) only lor high frequency radiation B) only for low frequency radiation

to de-Broglie wavelefrgth. The

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2 b. Obtain an expression for energy eigen value of a particle in a potential well of infiniteheight. (07 Marks)

c. Explain the most probable state of the particle by drawing probability curves. (05 Marks)d. The position and momentum of 2 kev electrons are simultaneously determined and if its

position is located within 0.12 nn, what is the percentage of uncertainty in its momentum=(04 Marks)

rr'3|' r' 3. Choose the correct answers for the following :

i) At very high temperatures, the mean collision time

A) 12 u,+ ., +

or an electron t, " gl|IiT.?

ii) If Fermi energy of a metal is 3 eV, its Fermi temperature is

A) 3'"5 r 104 K B) 1.6 x 102 K c) 3.5 , 103 K, '', " D) 10-12 Kiii) Current,of 3A is flowing through a cylindrical copper wire ofradius 3 mm. the current

density is nearlyA) 105 Nrl .:.,, B) 1or A/m2 c) 106 A/#

iv) Drift velocity of electrons in a metal depends on

D) independent of T

D) 10-6 A/m2

expression for(10 Marks)(06 Marks)

(04 Marks)

A) mass of eterman B) applied electric fieldC) mean collision time D) all of these

b. Define mean tree path. mean collision time and relaxation time. Derive anconductivity in metals.

c. Explain the merits of quantum free eleOtron theory.

4 a. Choose the correct answers for tfre,fof6wing 'i) The dipolemendent between the pair of opposite charges each of magnitude 1 pC

separated by a distance of l0 prm is

A) 10 x 10-12 cm B) 10-12 cm C) 10 x 1012 cm D) 10-12 cmiD The distance between plates of a parallel plate capacitor is doubled. The capacitance

A) doubledC) increases,by 4 times

iii) Relation,between magnetic flux(with uiual notations) is given by

iv)A)p:BH B) B: pH

" ;Barium titanate is an example ofA) ferromagnetic materialC) ferroelectric material

A) beam is less powerfulC) beam has large wavelength

B) halvedD) decreases by 4 times

density, permeability and magnetic field intensity

C) H: Bpr ' '

il; No relation exist"

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B) superconducting mateiialD) none of these

(06 Marks)(05 Marks)(05 Marks)

(04 Marks)

B) beam is highly powerfulD) none of these

b. Explain various electrical polarization mechanisms in dielectrics."c. What are ferroelectrics? Explain ferloelectric hysterisis.d. Briefly explain the paramagnetism phenomenon using Langevin's theory.

PART _ B5 a. Choose the correct answers for the following :

i) Pumping process in diode LASER is byA) optical means B) forward biasC) electrical discharge D) thermal means

i, Semiconductor LASER is not preferred in LASER drilling since






5 a. iii) Holograms can give a clear 3D image if they are observed underA) white lightB) green lightC) blue lightD) same wavelength of light used for recording the hologram.

ir) LASER beam is highly powerful due toA) high intensityC) constructive interference

A) high absorption lossC) not easily available

B) less broadeningD) all of these

C) insulator

,: B) low magnetic field,:. D) high resistance

B) high scattering lossD) none of these

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(04 Marks)

(04 Marks)

D) super conductor

(04 Marks)

(04 Marks)

D) 68%

c.

d.

With the necessary diagram, explain the construction and working of He-Ne LAS% Marks)

Wlf LASER is preferred for environmental pollution monitoring? Explain the principle andrelative merits of LIDAR system (05 Marks)Find the ratio between Einstein coefficients for stimulated and spontaneous transmissions in

a LASER system emitting light of wavelength 5000 A. ., ,:"'.,,.

6 a. Choose the correct answers for the followingi) If the critical temperature lor specimen is above 0 K. it must be

A) semiconductor B) conductorii) SQUID is used ro measure

A) high magnetic fieldC) high potential dilference

iii) Propagation of light ray in graded index fiber is byB) diffiaction

C) reflective confinement D) none of theseiv) Shorter wavelength radiations are not preferred in optical fibers due to

b. Explain type I and type II super conductors with necessary graph and example. (06 Marks)c. Obtain an expression for angle of acceptance and numerical aperture of an optical fiber.

Also explain the condition for light propagation in a optical fiber. (06 Marks)d. An optical fiber has core index of 1.6 and cladding index of 1.4 with core diameter of

40 pm. Calculate 'V' number ratio when the fiber is in air and;ih water of refractive index1.33. Given wavelength of light is 500 nm.

.. .'

a. Choose the correct answers for the following :

i) The atomic packing factor of NaCl crystalA) s2% B) r00%

ii) Four types of Bravasis lattices are observed inA) Rhombohedral structureC) Triclinic system

c) 74%

B) Monoclinic systemD) Orlhorhombic system

iii) Acrystalhas unit cellproperties a* b * c and cr: p:90o + B, isA) orthorhombic B) monoclinic C) tetragonal

iv) The Miller index of the plane parallel to Y-axis isA)(101) B)(01 1)

at a glancing angle of 30o, calculate the lattice constant.

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D) triclinic ..,1;;

D)(co 1 1)C)(1co1)b. Obtain an expression for interplanar spacing in a crystal in terms of lattice parameters.

(06 Marks)c. What is coordination number? Explain this with reference to SC, BCC and fcc structures.

(06 Marks)d' X-ray of wavelength 5 A interacts with a crystal. If the second order reflection was observed

eg$TFi.e.L, ggi:1,t",;l'ri"

(04 Marks)






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Engineering Physics Jan 2014