## Engineering Physics - Oct 2012

### First Year Engineering (Semester 1)

TOTAL MARKS:

TOTAL TIME: HOURS

### Answer any one question from Q1 & Q2

**1 (a)** Prove that in Newton?s Ring by reflected light the diameter of bright ring are proportional to the square root of the odd natural number.(6 marks)
**1 (b)** Explain any one application of Ultrasonic Waves.(3 marks)
**1 (c)** The average reverberation time of a hall is 1.5 sec. and the area of the interior surface is 3340m^{2}. If the volume of the hall is 13000m^{3}. Find the absorption coefficient.(3 marks)
**2 (a)** Explain how piezoelectric effect can be used for generating Ultrasonic Waves?(6 marks)
**2 (b)** Define fringe width for wedge shaped film, obtain an expression for it.(3 marks)
**2 (c)** Find the half angular width of the central maxima in the
fraunhofer diffraction pattern of slit having width 10 ?10^{-5} cm. When illumininated by light having wave length 5000 A?(3 marks)

### Answer any one question from Q3 & Q4

**3 (a)** State the Phenomena of Double Refraction. Hence explain Huygen?s Wave Theory of Double Refraction.(6 marks)
**3 (b)** Draw energy band picture for P-N junction in case of (i) Zero Bias (ii) Forward Bias (iii) Reverse Bias.(3 marks)
**3 (c)** A silver wire is in the form of a ribbon 0.5cm wide and
0.1 mm thick. When a current of 2A passes through the ribbon perpendicular to 0.8 Tesla Magnetic Field. Calculate the Hall Voltage produced.

(Given : Density of Silver = 10.5 gm/cc, Atomic Weight of
Silver = 108, Avogadros No. 6.02 ? 10^{23} gm/mole)(3 marks)
**4 (a)** Derive an expression for Conductivity in Semiconductor.(6 marks)
**4 (b)** Explain any one application of Laser.(3 marks)
**4 (c)** How should the Polarizer and Analyzer be oriented to reduce intensity of beam to (i) 50% (ii) 0.25 of its original intensity ?(3 marks)

### Answer any one question from Q5 & Q6

**5 (a)** Define Phase Velocity and Group Velocity. Hence obtain the relation between V_{p} and V_{g} for DeBroglie Wave.(6 marks)
**5 (b)** Explain the physical significance of ? and |?|^{2}.(4 marks)
**5 (c)** An electron is bounded by an infinite potential well of width 2 ?10^{-8}. Calculate the lowest two permissible energies of an electron.

(Give: h=6.64?10^{-34} J- sec., m=9.1 ? 10^{-31} kg)(3 marks)
**6 (a)** Derive Schroedinger?s Time Independent Wave Equation.(6 marks)
**6 (b)** State DeBroglie?s Hypothesis. Hence obtain the relation for DeBroglie?s Wave Length in terms of Energy.(4 marks)
**6 (c)** The position and momentum of 1 kev electron are simultaneously measured. If its position is located within 1A?. Find the percentage of uncertainty in its momentum.

(Given: h=6.64?10^{-34} J-sec., m=9.1?10^{-31} kg)(3 marks)

### Answer any one question from Q7 & Q8

**7 (a)** Explain the Phenomena of Super-conductivity. Explain
Type - I and Type - II Super-conductors.(6 marks)
**7 (b)** Explain any two applications of Nano-technology.(4 marks)
**7 (c)** Explain any two properties of Nano-particle.(3 marks)
**8 (a)** Explain Synthesis of Metal Nano-particle by Collidal Route Method.(6 marks)
**8 (b)** Explain BCS Theory of Super-conductivity.(4 marks)
**8 (c)** State and explain:

(i) Meissner Effect

(ii) Persistent Current(3 marks)