## Applied Physics 1 - Dec 2011

### 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.

### Answer any five :-

**1 (a)** Draw the following planes (121), (100), (111)(3 marks)
**1 (b)** State any three applications of superconductivity(3 marks)
**1 (c) ** How Lissajous figure are used to determine phase difference?(3 marks)
**1 (d)** What are ultrasonic waves? State magnetostriction effect.(3 marks)
**1 (e) ** State Sabine's formula.(3 marks)
**1 (f)** Calculate atomic packing factor for FCC crystal structure ?(3 marks)
**1 (g)** Show the position of Fermi level in intrinsic semiconductor, p-type semiconductor and n-type semiconductor.(3 marks)
**2 (a)** Explain Dimond crystal structure with proper diagram. Calculate the number of atoms per unit cell, atomic radius and atomic packing factor for diamond unit cell.(8 marks)
**2 (b)** What is cavitation effect? Kind the natural frequency of vibration of quartz plate of thickness 2mm,. Given: Young's modulus for quartz 8 x 10^{10} N/m^{2} and density 2650 kg/m^{3}. Calculate the change in thickness required if the same plate is to be used to produce ultrasonic waves of 3 MHz.(7 marks)
**3 (a)** Explain reverberation and reverberation time. Explain various methods for design of good acoustics.(8 marks)
**3 (b)** What is lattice parameters? Aluminium has density 2.7 gm/cm^{3}. It has atomic weight 27 and lattice parameter is 4.05 A?. Determine the type of crystal structure followed by Aluminium and calculate the atomic radius. Given Avogadro's number N_{A} = 6.023 x 10^{23}/gm mole.(7 marks)
**4 (a)** what is superconductivity and critical temperature? Descibe type I and type II superconductor.(8 marks)
**4 (b)** Define mobility of charge. Find resistivity of germanium at 300 ?K. Given density of carriers is 2.5 x 10^{19}/m^{2}. Mobility of electron is 0.39 m^{2}/V-Sec and mobility of hole is 0.19 m^{2}/V-Sec. Charge of electron is 1.6 x 10^{19}C.(7 marks)
**5 (a)** State Hall effect and what is the signification of hall effect? N-type Ge sample has donor concentration 10^{21} atoms/m^{3}. What hall voltage would you expect if current 1 x 10^{-3} A and if 0.5 magnetic field is applied across 2 mm thick sample.(8 marks)
**5 (b)** What is piezoelectric effect? Explain with neat labeled diagram the construction and working of Piezoelectric oscillator.(7 marks)
**6 (a)** State and explain terms in Bragg's law of X-ray diffraction. Calculate the glancing angle on cube (100) of rock salt having lattice constant 2.84 A? corresponding to first order diffraction maximum for X-ray of wavelength 1.541 A? (8 marks)
**6 (b)** Explain construction and working of CRO.(7 marks)

### Solve/Explain any three;

**7 (a)** A class room has dimension 20 x 15 x 10 m^{3}, the reverberation time is 3 sec. calculate total absorption of its surfaces and average absorption coefficient.(5 marks)
**7 (b)** Liquid crystal and different phase of liquid crystal (5 marks)
**7 (c) ** Point defects in crystal (5 marks)
**7 (d)** Meissner effect(5 marks)