Jawaharlal Nehru Technological University Anantapur 2009 B.Tech Regular s,e ENGINEERING PHYSIC set - 3 - Question Paper

Code No: 09A1BS02    R09    Set No. 3

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) Explain Fermi-Dirac distribution function. Illustrate the effect of temperature

on the distribution.

(b) Derive an expression for density of states of an atom.    [8+7]

2.    (a) Derive the expressions for:

i.    Acceptance angle and

ii.    Numerical aperture of an optical fiber.

	(b) Describe the different types of fibers by giving the refractive index profiles and
	propagation details.	[8+7]
3.	(a) What are Brillouin zones? Explain using E-K diagram.
	(b) Define effective mass of an electron. Explain its physical significance.
	(c) What is a hole? List out the properties of a hole.	[5+5+5]
4.	(a) Write notes on point defects in crystals..
	(b) Derive the expression for the density of Frenkel defects in a metallic crystal.
	(c) What is Burgers vector? Explain.	[5+5+5]
5.	(a) Describe the different methods of acoustic quieting.
	(b) Describe various method to achieve soundproofing.	[7+8]
6.	(a) Explain the terms:

i.    Magnetic induction,

ii.    Magnetic susceptibility,

iii.    Permeability of a medium and

iv.    Intensity of magnetization.

(b)    What are hard and soft magnetic materials? Give their characteristic properties and applications.

(c)    A paramagnetic material has a magnetic field intensity of 10⁴ amp/m. If the susceptibility of the material at room temperature is 3.7 x 10^-3. Calculate the magnetization and flux density of the material.    [6+5+4]

7. (a) What do you understand by Miller indices of a crystal plane?

(b)    Show that in a cubic crystal the spacing (d) between consecutive parallel planes of Miller indices (h k l) is given by d = a (h² + k² + l²)^-1/2.

(c)    NaCl crystals have FCC structure. The density of NaCl is 2.18 gm/cm². Calculate the distance between two adjacent atoms. (Molecular weight of NaCl = 58.5).    [4+7+4]

8. (a) Derive an expression for density of electrons in intrinsic semiconductors.

(b)    Explain the variation of Fermi level with temperature in the case of p-type semiconductors.

(c)    If the effective mass of holes in a semiconductor is 5 times that of electrons, at what temperature would the Fermi level be shifted by 15% from the middle of the forbidden energy gap? [Given that the energy gap for the semiconductor is 1.20 eV].    [7+4+4]

8

Attachment: jawaharlal-nehru-technological-university-anantapur-2009-b-tech-37850-1.pdf

Earning:   Approval pending.