Question 9

TUTORIAL SESSION 26-11-2008
MODEL QUESTION PAPER

MAXIMUM TIME: 1 HOUR MAXIMUM MARKS: 25
Answer any two questions

I (a) Obtain an expression for energy density of photons in terms of Einstein’s coefficients. (8 Marks)
(b) Explain the working of He-Ne laser. (4½ Marks)

II (a) Using total internal reflection concept, obtain an expression for the acceptance angle and numerical aperture in an optical fibre. (5 Marks)
(b) Explain BCS theory of superconductivity. (3 Marks)
(c) What is attenuation in optical fibre? Explain the attenuation mechanisms.
(4½ Marks)

III (a) What are miller indices? (3 Marks)
(b) Explain with neat sketch the NaCl crystal. (5 Marks)
(c) Explain how Bragg’s spectrometer can be used to determine the interplanar spacing. (4½ Marks)

IV (a) Write a brief note on fabrication technology of nanomaterials. (2½ Marks)
(b) Describe a method of measuring the velocity of ultrasonic waves in solids. (5 Marks)
(c)Explain how an acoustic grating is used to determine the velocity of ultrasonic waves in liquid. (5 Marks)