Question Paper: Sem-1 Applied Physics- I May 17
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## Applied Physics - I May 17

### First Year (Semester 1)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Draw neat diagrams wherever necessary.
(4) Figures to the right indicate full marks.

Q1) Attempt any five (15 marks)

1(a) Justify us of X-rays in the study of crystals.
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1(b) Draw the following [231],(213),(102).
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1(c) Derive APF for FCC
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1(d) Describe Magnetostriction effect.
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1(e) The resistivity of Cu is $1.72 \times 10 ^ {-28}$ $m^{-3}$. Calculate the mobility of electrons in Cu. Given that number of electrons per unit volume is $10.41 \times 10^{28}$ $m^{-3}$.
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1(f) What is cavitation?
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2(a) What is Fermi level? Show that it is locate at the Center of forbidden energy gap. Find the resistivity of Cu assuming that each atom contributes one free electron.Consider density = 8.96 gm/ cubic cm, Atomic weight = 63.5, mobility of electron = 43.3 cm2/ V-sec.
(8 marks) 00

2(b) Calculate APF for HCP structure.
(7 marks) 00

3(a) Derive Bragg’s law and using it calculate the smallest glancing angle at which X- rays of 1.549 Angstrom will be reflected from a crystal having spacing of 4.255 Angstrom.
(8 marks) 00

3(b) A metal ring having cross section 5 cm2 and diameter of 20 cm has a coil of 200 turns wound over it. Determine the current required to produce flux of 4 milli weber. Consider the metal with relative permeability as 380.
(7 marks) 00

4(a) Explain with neat diagram different phases of liquid crystal. State any two applications of liquid crystals.
(5 marks) 00

4(b) Explain in detail “electronic polarization”
(5 marks) 00

4(c) Define the term “mobility” Write any formulas to obtain it. Write its unit.
(5 marks) 00

5(a) Explain the principle of solar cell. What are the main features of its construction?
(5 marks) 00

5(b) What are the conditions of good acoustics? Give some methods to design a hall with good acoustics.
(5 marks) 00

5(c) Derive critical radius ratio for ligancy 6.
(5 marks) 00

6(a) Explain how to produce ultrasonic waves with the help of piezoelectric effect.
(5 marks) 00

6(b) What is Hall Effect? How to find carrier concentration using it in semiconductors?
(5 marks) 00

6(c) Calculate reverberation time for an empty hall of size $21 \times 16 \times 10$ m3 with absorption Coefficient 0.106.
(5 marks) 00