Question Paper: Applied Physics 1 : Question Paper Dec 2015 - First Year Engineering (Semester 1) | Mumbai University (MU)
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## Applied Physics 1 - Dec 2015

### First Year Engineering (Semester 1)

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) Draw the unit cell and Basic of DC structure.(3 marks) 1 (b) Draw the following w.r.t. a cubic unit cell:
(1 1 1) (1 1 1) (1 2 3).
(3 marks)
1 (c) Draw a neat labelled Energy band diagram to show the variation of Fermi Level with doping concentration in N-Type semi-conductors.(3 marks) 1 (d) Calculate electronic polarizability of Argon atom. Given relative permittivity is 1.0024 at NTP and the gas contains 2.7 × 1025 atoms per m3.(3 marks) 1 (e) What are the properties of soft magnetic materials? Briefly explain one application.(3 marks) 1 (f) Monochromatic high energy x-rays are incident on a crystal. If 1st order reflection is observed at an angle 3.4°, at what angle would 2nd order reflection be expected.(3 marks) 1 (g) A class room has dimensions 20 × 15 × 5 m3. The reverberation time is 3.5 sec. Calculate the total absorption of its surface and average absorption coefficient.(3 marks) 2 (a) Draw the unit cell of HCP. Derive the number of atoms/ unit cell, the c/a ration and the packing fraction. Calculate the ratio of the number of vacancies to the number of atoms when the average energy required to create a vacancy is 0.95 ev at 500k.(8 marks) 2 (b) Explain Hall effect & its significance. With a neat diagram derive the expression for the hall voltage & Hall co-efficient.(7 marks) 3 (a) Draw the hysteresis loop for a ferromagnetic material. Prove that in a ferromagnetic material, the power loss / unit volume in a hysteresis cycle is equal to the area under the hysteresis loop.
A solenoid consisting of 500 turns and carrying 5amp is 0.5 long. Calculate (i) magneto motive force & (ii) Total flux if the area of the cross section in 0.0004 m2. (Assume the medium is air).
(8 marks)
3 (b) With a neat labelled diagram explain the principle, construction and working of a piezoelectric oscillator.(7 marks) 4 (a) Explain analysis of crystal structure using Bragg's X-ray spectrometer.(5 marks) 4 (b) An Ultrasonic beam of 1 cm wavelength sent by a ship returns from sea bed after 2 sec. If the salinity of sea water at 30°C is 29 gm/lit. Calculate the depth of sea bed at 30°C and the frequency of ultrasonic beam.(5 marks) 4 (c) Explain Critical Configuration & find the Critical radius ratio of an ionic crystal for ligancy 6.(5 marks) 5 (a) Explain ionic polarization & derive the expression for ionic polarizability.(5 marks) 5 (b) In a solid, consider the energy level lying 0.012ev below Fermi level. What is the probability of this level not being occupied by an electron?
Given T=300 Kelvin. Ks=1.38×10-23 j/K.
(5 marks)
5 (c) For an intrinsic semiconductor show that the Fermi level lies in the center of the forbidden energy gap.(5 marks) 6 (a) What is reverberation? Define Reverberation time. Explain its role in acoustics.(5 marks) 6 (b) Explain the principle, construction & working of a LED.(5 marks) 6 (c) Describe the types of liquid crystal & their properties.(5 marks)

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