B.Sc. VI - Semester Examination
BS-VIS/5
26727
PHYSICS
Course No. : 601
Time Allowed-3 Hours Maximum Marks-80
Note: Attempt five questions, selecting one from each unit.
Unit - I
1. A) In a phase shift oscillator R = RL = 1MΩ and C = 75pF. At what frequency does the circuit oscillate? (4)
B) Describe distortion and noise in amplifiers. How does negative feedback reduce distortion and noise? (12)
OR
2. A) Draw the circuit diagram of Hartley Oscillator and explain its principle. (4)
B) What is the use of coupling in amplifiers? Draw a diagram of the RC-coupled amplifier. Discuss and explain its frequency response curve. (12)
Unit - II
3. A) In a crystal, a lattice plane cuts intercepts of 2a, 3b, and 6c along the three axes where a, b and c are primitive vectors of the unit cell. Determine the Miller indices of the given plane. (4)
B) Describe the powder method of x-ray diffraction and explain how it used in the determination of crystal structure? (12)
OR
4. A) Calculate Bragg angle for x-rays having wavelength 1.54Å for first order if the interplanar spacing is 2.67Å. (4)
B) State and prove Bragg’s law of x-ray diffraction. (12)
Unit - III
5. A) What are type I and type II super-conductors? (4)
B) What are the assumptions of Debye theory of specific heat of Solids? Derive an expression for the lattice specific heat according to Debye model. (12)
OR
6. A) What are point defects in crystals? Discuss Frenkel defect. (4)
B) Give an account of the quantum theory of paramagnetism and derive an expression for magnetic susceptibility. (12)
Unit - IV
7. A) A substance shows a Raman line at 4567Å when exciting line 4358Å is used. Deduce the position of stokes and anti-stokes line for that substance when exciting line 4047Å is used. (4)
B) Give an experimental arrangement of Raman Effect. Explain the origin of stokes and anti-stokes line in Raman Effect on the basis of quantum theory. (12)
OR
8. A) Explain any four applications of optical fibres. (4)
B) What is dispersion in optical fibre? Explain various mechanisms that contribute to dispersion. (12)
Unit - V
9. A) Explain why laser action cannot occur without population inversion between atomic levels. (4)
B) Discuss Einstein's coefficients. Derive the relation between them. (12)
10. A) What is the difference between laser light and ordinary light. (4)
B) What do you mean by laser pumping? Explain three level and four level pumping schemes for laser action. (12)
