Bharathiar University 2007 M.Phil Advanced Physics MP 3128 -e - Question Paper

M.Phil. Advanced Physics MP 3128 May-June 2007

Time : 3 hours Maximum : 100 marks
ans any 5 ques..
every ques. carries 20 marks.
(5 * 20 = 100)
1. Quantize the non-relativistic Schrödinger formula for fermions of mass m moving in potential field.
2. Quantize electromagnetic field in free space and develop the concept of photon as a entity carries discrete amount of energy and momentum.
3. What is meant by localized bonds? discuss in detail about the merits and demerits of various theories.
4. (a) Mention advantages of optical fiber as waveguide over conventional metallic waveguide. (10)
(b) A silica optical fiber has a core refractive index of 1.50 and a cladding refractive index of 1.47. Determine,
(i) the critical angle at the core cladding interface,
(ii) the N.A. for the fiber and
(iii) the acceptance angle in air for the fiber. (10)
5. (a) Discuss the various scattering losses in SiO2 fiber at the operating wavelengths. (15)
(b) Calculate the total number of guided modes propagating in the multimode step index fiber having diameter of 50 m and numerical aperture of 0.2 and operating at a wavelength of one m. (5)
6. (a) Mention any 4 needed properties of light sources used in the optical communication. (5)
(b) What are direct band gap and indirect band semiconductors? provide example. (10)
(c) Why do we prefer laser diodes over LEDs for communication applications? (5)
7. (a) Discuss the various mechanisms involved to produce laser emission. (5)
(b) Describe the construction and working of Nd YAG laser. (15)
8. (a) Estimate the power delivered to various kinds of fibers with respect to LEDs. (5)
(b) Why laser emission is not found in atomic system under thermal equilibrium? (7)
(c) Explain RZ and NRZ coding and their effects on bit rate. (8)

Earning:   Approval pending.