Applied Physics 2 - Dec 2012

First Year Engineering (Semester 2)

TOTAL MARKS: 60
TOTAL TIME: 2 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Use suitable data wherever required.
(4) Figures to the right indicate full marks.

Attempt any five from the following:-

1 (a) Explain why we see beautiful colour in thin film when it is exposed to sunlight.(3 marks) 1 (b) Why would you recommend use of optical fibre in communication system?(3 marks) 1 (c) Draw the energy level diagram of He-Ne laser. What is its wavelength in visible range? (3 marks) 1 (d) Calculate the De-Broglie wavelength of proton travelling with a velocity equal to 1/20^th velocity of light.
(Mass of proton = 1.674 x 10^-27kg)(3 marks) 1 (e) The susceptibility of a paramagnetic material at 300 K is 3.7x10^-3. Find its relative permeability at 300 K.(3 marks) 1 (f) State and explain Ohm's law for magnetic circuit.(3 marks) 1 (g) Define and name different ranges of vacuum in terms of pressure.(3 marks) 2 (a) Explain with neat figure construction and working of Rotary pump. For which vacuum range is it used? (8 marks) 2 (b) Write full form of LASER. Explain three main processes involved in the production of LASER with appropriate figures. (7 marks) 3 (a) Derive the formula for numerical aperture for a step index fibre. Calculate the Acceptance angle for an optical fibre given that refractive index of core is 1.45 and refractive index of cladding is 1.4.(8 marks) 3 (b) Explain the construction and working of semiconductor diode laser with proper sketches. What are merits and demerits of this laser? (7 marks) 4 (a) In a Newton's ring experiment the diameter of the 10^th dark ring changes from 1.4 cm to 1.27 cm when a liquid is introduced between the lens and the plate. Calculate the refractive index of the liquid. (5 marks) 4 (b) Using the uncertainty principle show that an electron cannot pre-exist in free state in a nucleus.(5 marks) 4 (c) A solenoid consisting of 500 turns and carrying 4 Amp current is 0.5 m long. Calculate:
(i) Magnetomotive force
(ii) Flux density B (5 marks) 5 (a) A diffraction grating used at normal incidence gives a line 5400Å in certain order super-imposed on another line 4050Å of the next higher order. If the angle of diffraction is 30°, how many lines/cm are there on the grating?(5 marks) 5 (b) Derive one dimensional time dependent Schrodinger equation for matter waves.(5 marks) 5 (c) Explain construction and working of Atomic force microscope.(5 marks) 6 (a) Explain the experimental method of determination of wavelength of spectral line using diffraction grating. (5 marks) 6 (b) An electron is bound in one dimensional potential box with width 2.5Å. Assuming the height of the box to be infinite, calculate the first two permitted energy values of the electron. (5 marks) 6 (c) Discuss the importance of molecular modelling in bio-physics study.(5 marks) 7 (a) White light falls normally on a soap film of thickness 5x10^-5cm and of refractive index 1.33. Which wavelength in the visible region will be reflected most strongly? (5 marks) 7 (b) How the phenomenon of holography can be explained with interference and diffraction of light? (5 marks) 7 (c) What are hard and soft magnetic materials? Explain these materials using their characteristic properties and applications. (5 marks)