Download 182 101-SEM I

C 3908
B.E./B.Tech. DEGREE EXAMINATION, JANUARY 2009
Second Semester
Civil Engineering
PH 2111 – ENGINEERING PHYSICS – I
(Common to all branches B.E./B.Tech.)
(Regulation 2008)
Time: Three hours
Maximum : 100 marks
Answer ALL questions
PART A – (10 X 2 = 20 marks)
1. What is sonar? Mention two applications of it.
2. A ultrasonic generator consists of a quartz plate of thickness 0.7 mm and density 2800 kg/m3.
Find the fundamental frequency of ultrasonic waves if the Young’s modulus of quartz is 8.8 x 10
10
N/m2.
3. Define population inversion and metastable state.
4. What are the advantages of heterojunction semiconductor laser over homojunction?
semiconductor laser?
5. Distinguish between step index and graded index fiber.
6. A silica optical fiber has a core refractive index of 1.5 and cladding refractive index of 1.47.
calculate the critical angle at he core-cladding interface.
7. What is Compton wavelength and calculate its value.
8. What is the physical significance of wave function .
9. State the values of coordination number of HCP structure and diamond structure.
10. The lattice constant for a FCC structure is 4.938A0. Calculate the interplanar spacing of (220)
planes.
PART –B (5X16=80marks)
11. (a) (i) What is inverse Piezo electric effect?
(ii) Describe the construction and working of a piezo electric generator to produce ultrasonic
waves.
(iii) State the merits and demerits of magnetostriction oscillator. (2+10+4)
OR
(b) (i) What is acoustic grating?
(ii) Describe the method of determining the velocity of ultrasonic waves using acoustic
grating.
(iii) Mention any four applications of ultrasonic waves.
(2+10+4)
12. (a) (i) Distinguish between spontaneous and stimulated emission of radiation.
(ii) Describe the construction and working of He-Ne laser with energy level diagram.
(iii) What are Einstein’s A and B coefficients? (4+10+2)
OR
(b) (i)Describe the Vibrational modes of CO2 molecule.
(ii) Describe the construction and working of CO2 laser with energy level diagram.
(iii) For a semiconductor laser, the band gap is 0.8eV. what is the wavelength of light emitted
from it. (3+10+3)
13. (a) (i) Define acceptance angle and numerical aperture.
(ii) Derive the expression Sin n12 – n22.
(iii) Describe a method of measuring the temperature of a source using fiber optic sensor.
(2+8+6)
OR
(b) (i) Describe a fiber optic communication system.
(ii) Describe the principle, construction and working of light emitting diode.
(iii) State the advantages of light emitting diodes in electronic display. (6+8+2)
14. (a) (i) What is Compton effect?
(ii) Derive an expression for the wavelength of scattered X ray photon from a material.
(iii) A X ray photon of wavelength 1.24 x 10-3A0 is scattered by a free electron through an
angle 900. Calculate the energy of the scattered photon. (2+10+4)
OR
(b) (i) Derive the Schrodinger’s time independent wave equation.
(ii) Apply Schrodinger’s wave equation to a particle in one-dimensional box and calculate the
Eigen value and Eigen function. (8+8)
15. (a) (i) What are Bravais lattice?
(ii) Derive an expression for the interplanar spacing in a cubic structure.
(iii) With a neat diagram describe the edge dislocation. (2+8+6)
OR
(b) (i) Define Atomic radius and packing fraction.
(ii) Describe a HCP structure. Show that for an HCP structure c/a =  8/3 and hence calculate
the packing fraction for the HCP structure.
(iii) The lattice constant of a metal with cubic lattice is 2.88 A0. The density of metal is 7200
Kg/m3. calculate the number of unit cell present in 1Kg of the metal.