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**B.E/B.Tech DEGREE EXAMINATION, Jan 2009**

**First Semester**

**PH2111 – Engineering Physics-I**

**(Regulation 2009)**

**Time : 3 hours Maximum Marks:100**

**PART A (10 x 2 = 20 MARKS )**

1) What is sonar? Mention 2 applications of it.

2) A ultrasonic generator consists of a quartz plate of thickness 0.7 mm and density kg/m3 Find the fundamental frequency of ultrasonic waves if the Young’s modulus of quartz is 8.8 x 1010 N/m2.

3) Define population inversion and metastable state.

4) What are the advantages of hetrojunction semiconductor laser over homojunction semiconductor laser?

5) Distinguish between step index fiber and graded index fiber.

6) A silica optical fiber has a core refractive index of 1.50 and a cladding refractive index of 1.47. Calculate the critical angle at the core-cladding interface.

7) What is Compton wavelength and calculate its value.

8) What is the physical significance of wave function of ?

9) State the values of coordination number for HCP structure and diamond structure.

10) The lattice constant for a FCC structure is 4.938 A0 Calculate the interplanar spacing of (220) planes.

**PART B (5 x 16 = 80 MARKS )**

11. (a) (i) What is inverse piezo electrict effect?

(ii) Describe the construction and working of a piezo electric generator to produce ultrasonic waves.

(ii) State the merits and demerits of magnetostriction oscillator.

OR

(b) (i) What is acoustic grating

(ii) Describe the method of determining the velocity of ultrasonic waves using acoustic grafting.

(iii) Mention any four applications of ultrasonic waves.

12. (a) (i) Distinguish between spontaneous emission and simulated 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?

OR

(b) (i) Describe the vibrational modes of CO2 laser with energy level diagram.

(ii) Describe the vibrational modes of CO2 molecule.

(ii) Describe the construction and working of CO2 molecule.

(iii) For a semiconductor laser, the band gap is 0.8 eV. What is the wavelength of light emitted from it.

13. (a) (i) Define Acceptance angle and Numerical aperture

(ii) Derive the expression sin = 8

(iii)Describe a method of measuring the temperature of a source using fiber optic sensor.

OR

(b) (i) Describe a Fiber optic communication system.

6 (ii) Describe the principle, construction and working of light emitting diode.

(iii) State the advantages of light emitting diodes in electronic display

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 -2 A is scattered by a free electron through an angle of 90o. Calculate the energy of the scattered photon.

OR

(b) (i) Derive the Schroedinger’s time independent wave equation.

(ii) Apply Schroedinger wave equation to a particle in one dimensional box and calculate the eigen value and eigen function

15. (a) (i) What are Baravais lattice?

(ii) Derive an expression for the interplanar sparing in a cubic structure.

(iii) With a neat diagram describe the edge dislocation.

OR

b) (i) Define Atomic radius and packing fraction.

(ii) Describe a HCP structure. Show that for an HCP structure c/a = and hence calculate the packing fraction for the HCP structure.

(iii) The lattice constant of a metal with cubic lattice is 2.88 Ao. The density of metal is 7200 kg/m3 . Calculate the number of unit cell present in 1 kg of the metal.

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