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