# Applied Physics 1 CBCGS 2017-2018 BE IT (Information Technology) Semester 1 (FE First Year) Question Paper Solution

Applied Physics 1 [CBCGS]
Date: December 2017

1) Question no 1 is compulsory

2) Attempt ant three questions from Q.2 to Q.6 .

 1 | Attempt ant five
 1.a

‘Crystal acts as three dimensional grating for X-rays’, explain.

Concept: X-ray Diffraction
Chapter:  Crystal Structure
 1.b

Calculate the frequency and wavelength of photon whose energy is 75eV.

Concept: De Broglie Wavelength
Chapter:  Quantum Mechanics
 1.c

Draw the energy band diagram  of p-n junction diode in forward and reverse bias condition .

Concept: Fermi Level Diagram for P-N Junction
Chapter:  Semiconductor Physics
 1.d

“Superconductor is a perfect diamagnetic”, Explain.

Concept: Meissner Effect
Chapter:  Superconductivity
 1.e

What is reverberation time? How it is important ? write the factors affecting reverberation time.

Concept: Reflection of Sound(Reverberation and Echo)
Chapter:  Acoustics
 1.f

A quartz crystal of thickness 1.5 mm vibrating with resonance. Calculate it’s fundamental frequency if the Young’s modulus of quartz crystal is 7.9×1010N/m2 and density is 2650 kg/m3

Concept: Study of characteristics of unit cell of Diamond, ZnS, NaCl and HCP;
Chapter:  Crystal Structure
 1.g

Mobility of electron and hole in a sample of Ge at room temperature are 0.36 m2 /V-sec and 0.17m2 /V-sec respectively. If electron and holes densities are equal and it is 2.5 ×1013 /cm3 , calculate its conductivity.

Concept: Conductivity, mobility, current density (drift & diffusion) in semiconductors(n type and p type)
Chapter:  Semiconductor Physics
 2
 2.a

With Heisenberg’s uncertainty principle prove that electron cannot survive in nucleus. An electron has a speed of 300m/sec. with uncertainty of 0.01% . find the accuracy in its position.

Concept: Heisenberg’S Uncertainty Principle
Chapter:  Quantum Mechanics
 2.b

Show that fermi energy level in intrinsic semiconductor is at the Centre of forbidden energy gap. What is the probability of an electron being thermally excited to the conduction band in Si at 30℃. The band gap energy is 1.12 eV.

Concept: Fermi Energy Level in Intrinsic Semiconductors
Chapter:  Semiconductor Physics
 3
 3.a

With neat diagram of unit cell , explain the structure of HCP crystal and calculate the no. of ions per unit cell, co ordination no., lattice constant and packing factor of the structure.

Concept: Study of characteristics of unit cell of Diamond, ZnS, NaCl and HCP;
Chapter:  Crystal Structure
 3.b

State the Hall effect. Derive the expression for Hall voltage and Hall coefficient with neat diagram.

Concept: Hall Effect
Chapter:  Semiconductor Physics
 4
 4.a

What is the working principle of maglev? Explain how it can acquire high speed?

Concept: Applications of superconductors- SQUID, MAGLEV
Chapter:  Superconductivity
 4.b

A hall of dimension 25×18×12m3 has an average absorption coefficient 0.2. find the reverberation time. If a curtain cloth of area 150m2 is suspended at the  centre of Hall with coefficient of absorption 0.75, What will be the reverberation
time?

Concept: Reflection of Sound(Reverberation and Echo)
Chapter:  Acoustics
 4.c

State the piezoelectric effect. With neat circuit diagram explain the principle and working of piezoelectric oscillator .

Concept: Piezoelectric Oscillator
Chapter:  Ultrasonics
 5
 5.a

With energy band diagram ,explain the variation of fermi energy level with temperature in extrinsic semiconductor .

Concept: Fermi energy level in extrinsic semiconductors
Chapter:  Semiconductor Physics
 5.b

Explain with example how to determine crystal structure by Bragg’s X-ray spectrometer.

Concept: Bragg’S Law
Chapter:  Crystal Structure
 5.c

Obtain one dimensional time dependent time independent Schrodinger equation.

Concept: Schrodinger’S Time Dependent Wave Equation
Chapter:  Quantum Mechanics
 6
 6.a

Concept: Study of characteristics of unit cell of Diamond, ZnS, NaCl and HCP;
Chapter:  Crystal Structure
 6.b

What is the significance of wave function ? derive the expression for energy eigen values for the free particle in one dimensional potential well.

Concept: Wave Function
Chapter:  Quantum Mechanics
 6.c

What is photovoltaic effect? Explain the principle and working of solar cell.

Concept: Applications of semiconductors : Rectifier diode, LED, Zener diode, Photo diode, Photovoltaic cell, BJT, FET, SCR., MOSFET
Chapter:  Semiconductor Physics

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