University of Mumbai 2008-1st Sem B.E FE Applied Physics I - Question Paper
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(REVISED COURSE)
(2 Hours) [Total Marks : 75
N.B.(1) Question No 1 is compulsory.
(2) Attempt any four questions from Question Nos. 2 to 7.
(3) Assume any suitable data wherever required.
(4) Figures to the right indicate full marks.
(51 Illustrate your answer with sketches wherever necessary . />/ r , JT
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1. (a) Explain various axes of quartz crystal. 3
(b) Define reverberation time. Write Sabine's Formula and explain the terms used in it. 3
(c) Explain Schottky defect and Frenkel defect in ionic crystal. 3
(d) Find the resistivity of intrinsic Ge at 300K. Given the density of carriers as 2*5 x 1019 rrr3. 3 (Given ji8 = 0*39 m2/volt-sec
Hh = 0*19 m2 /volt-sec.
(e) Define superconductivity, critical temperature and critical magnetic field Hc. 3
2. (a) Describe NaCI structure and calculate the number of molecules per unit cell and packing 8 factor assurring radius of Na+ is 0-98 A0 and radius of Cl" is 1-81 A.
(b) What is SONAR ? Find the depth of sea water from a ship or the sea surface if the time 7 interval of two seconds is required to receive the signal back.
Given that temperature of sea water is 20C and salinity is 10 gm/lit.
3. (a) What is Hall sffect ? Derive the expression for Hall cofeficient (RH) and Hall voltage (VH) 8 with proper ciagram,
(b) The volume of room is 600 m3. The wall area of the room is 220 m2, the floor area is 7 120 m2 and the ceiling area is 120 m2. The average sound absorption coefficient
(i) For the wall is 0 03
(ii) For the ceiling is 0*8
(iii) The floor it is 0-06.
Calculate the average sound absorption coefficient and the reverberation time.
4. (a) What is Meissner effect ? Explain the concept of MAGLEV Irains. 8 (b) An X-ray machine has an accelerating potential of 25000 V. Find the shortest wavelength 7
in the X-ray spectrum. Also evaluate its frequency as well as the energy of the photon. (Given Planks constant h = 6-63 x 10 34 J.sec.)
5. (a) Explain the basic principle of magnetostatic focussing. An electron travels with a velocity 8
of 2-5 x 106 m/s in vacuum in a uniform magnetic field strength of 0-94 x 101 wb/m2, such that velocity vector makes an angle of 30 with the field direction Determine the distance covered along the magnetic induction lines in five such revolution.
(b) What are continuous X-rays ? The interplanar spacing of (110) plane is 2 A for a FCC 7 crystal. Find the atomic radius.
6. (a) Explain functions of various important parts of a CRT with diagram. 8
(b) Derive packing factor for FCC. Cu has FCC structure and atomic radius 1-28 A. Calculate 7
its density if ts atomic weight is 63*5.
(Given Avogadros number = 6*023 x 103 In CGS).
(a) How does tne Fermilevel change with increasing temperature in the extrinsic 8
semiconductors (n-type and p-type) ? Sketch the diagram.
(b) Find the thickness of quartz plate needed to produce ultrasonic waves of frequency 7
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