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Engineering Physics : Question Paper Dec 2015 - First Year Engineering (Semester 1) | Pune University (PU)

## Engineering Physics - Dec 2015

### First Year Engg (Semester 1)

TOTAL MARKS:
TOTAL TIME: HOURS

### Solve any one question from Q1 and Q2

1 (a) Prove that in Newton's rings by reflected light the diameter of dark ring is proportional to square root of a natural number.(6 marks) 1 (b) Explain any two factors affecting the acoustics of a hall and remedies on that.(3 marks) 1 (c) The classroom has dimension, 20×15×5 m3. The reverberation time is 3.5 sec. Calculate the total absorption of its surface and the average absorption.(3 marks) 2 (a) Explain piezoelectric effect. Explain how piezoelectric oscillator is used to produce ultrasonic waves, with the help of a neat circuit diagram.(6 marks) 2 (b) The resultant amplitude of a wave when monochromatic light is diffracted from a single slit is $E_\theta = E_m = \dfrac {\sin \alpha }{\alpha}$. Then derive the condition of minima.(3 marks) 2 (c) A soap film having refractive index 1.33, and thickness 5×10-5 cm is viewed at an angle of 35° to the normal. Find the wavelength of light in the visible spectrum which will be absent from the reflected light.(3 marks)

### Solve any one question from Q3 and Q4

3 (a) Explain construction and working of Ruby Laser with the help of energy level diagram.(6 marks) 3 (b) What is Fermi level? Explain Fermi-Dirac probability distribution function.(3 marks) 3 (c) Plane polarized light of wavelength 5×10-5 cm is incident on a piece of quarter cut parallel to the optic axis. Find the least thickness of quarter for which the O-ray and E-ray combine to from plane polarized light.
Given: μ0=1.5442, μe=1.5633.
(3 marks)
4 (a) Explain Hall Effect. Derive the equation of Hall voltage and Hall coefficient.(6 marks) 4 (b) State and prove Malus law.(3 marks) 4 (c) Calculate the number of acceptors to be added to a germanium sample to obtain the resistivity of 20 Ω cm.
Given: μ=1700cm2/V.sec.
(3 marks)

### Solve any one question from Q5 and Q6

5 (a) Deduce Schr�dinger's time independent wave equation.(6 marks) 5 (b) Define phase (wave) velocity. Show that the phase velocity of matter wave is greater than the velocity of light.(4 marks) 5 (c) Calculate the deBroglie wavelength of electron of energy 1 keV.(3 marks) 6 (a) State Heisenberg's uncertainty principle and prove it by thought experiment of electron diffraction at a single slit.(6 marks) 6 (b) What is wave function? Explain what is normalization of wave function.(4 marks) 6 (c) The lowest energy of an electron trapped in a rigid box is 4.19 eV. Find the width of the box in A.U.(3 marks)

### Explain:

7 (a) (i) Critical field.(3 marks) 7 (a) (ii) Meissner effect.(3 marks) 7 (b) Explain any two properties of nano-particles in brief.(4 marks) 7 (c) Explain the applications of nano-particles in electronic industry.(3 marks) 8 (a) Explain the synthesis of nano-particles by chemical method in colloidal form with diagram and example.(6 marks) 8 (b) Explain in brief the BCS theory of superconductivity.(4 marks) 8 (c) Give any six applications of superconductivity.(3 marks)