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Jawaharlal Nehru Technological University Anantapur 2009 B.Tech Regular s,e ENGINEERING PHYSIC set - 4 - Question Paper

Wednesday, 29 May 2013 05:05Web

Code No: 09A1BS02    R09    Set No. 4

I B.Tech Regular Examinations,June 2010 ENGINEERING PHYSICS Common to CE, ME, CHEM, BME, IT, MECT, MEP, AE, BT, AME, ICE, E.COMP.E, MMT, ETM, EIE, CSE, ECE, EEE Time: 3 hours    Max Marks: 75

Answer any FIVE Questions All Questions carry equal marks

1.    (a) Obtain an expression for Fermi energy at T > 0 K.

(b)    Derive an expression for density of states of electrons.

(c)    Write short notes on:

i.    De Broglie wavelength and

ii.    Heisenbergs uncertainty principle.    [4+7+4]

2.    (a) Derive Braggs law of crystal diffraction.

(b)    Describe, in detail, Debye-Scherrer method for the determination of crystal parameter.

(c)    A certain crystal reflects monochromatic X-rays strongly when Braggs angle is 210 for the second order diffraction. Calculate the glancing angle for third order spectrum.    [4+7+4]

3.    (a) What is bonding in solids? Write the list of different types of bonding in


(b)    Describe with suitable examples, the formation of covalent and Vander-Waals bonds in solids.

(c)    What is bonding energy of a molecule? Explain.    [4+7+4]

4.    (a) Describe the top-down methods by which nanomaterials are fabricated.

(b) Explain how X-ray diffraction can be used to characterize nanoparticles.[9+6]

5.    (a) Discuss the propagation mechanism of light waves in optical fibers.

(b)    Derive the expression for the numerical aperture of an optical fiber.

(c)    A step index fiber has a numerical aperture of 0.16, and core refractive index of 1.45. Calculate the acceptance angle of the fiber and the refractive index of the cladding.    [5+6+4]

6.    (a) Using Kronig-Penney model show that the energy spectrum of an electron

contains a number of allowed energy bands separated by forbidden bands.

(b) Define effective mass of an electron. Explain its physical significance. [9+6]

7.    (a) Show that the application of forward bias voltage across p-n junction causes

an exponential increase in number of charge carriers in opposite regions.

(b)    Write notes on Liquid Crystal Display.

(c)    The current in a p-n junction at 270C, is 0.18 when a large reverse bias voltage is applied. Calculate the current when a forward bias of 0.98 V is applied.    [7+4+4]

8. (a) Define the terms magnetic induction (B), magnetization (M) and magnetic field (H). Obtain an expression relating to these quantities.

(b)    What are ferrites? Prove that ferrites are superior to ferro-magnetic materils. Write the applications of ferrites.

(c)    The magnetic susceptibility of aluminum is 2.3 x 10-5. Find its permeability and relative permeability.    [6+5+4]



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