Coimbatore - 641 107.
(2015 -2016)
(Common to all branches)
1.
What is the principle behind the LASER ? (#)
Explain the principle behind the LASER. (#)
2.
Define Stimulated absorption. (*)
Give explanation for stimulated absorption.
(@)
What is meant by stimulated absorption ?
(*)
3.
Difference between spontaneous and stimulated emission. (^)
Distinguish between spontaneous and stimulated emission.
(^)
Compare spontaneous and stimulated emission.
( @)
4.
What are the conditions necessary for laser action? (*)
Mention the necessary condition for laser action. (*)
What are the conditions involved in laser action.
($)
5.
What is meant by normal population and population inversion ? (*)
How do you achieve population inversion? (#)
Relate normal and inverse population inversion. (^)
6.
What is pumping action? Mention the different methods of it . (*)
Justify pumping action.
(@)
7. Can two level systems be used for the production of laser? Explain. (^)
8. Explain the characteristics (properties) of laser ? (#)
Mention the characteristics of laser.
(*)

9. Distinguish between ordinary and laser light. (^)
Compare ordinary and laser light.
(^)
Distinguish between ordinary and laser light.
(@)
10. What is optical resonant cavity? Mention its function. (*)
Explain function involved in optical resonant cavity.
(^)
Give explanation for function of optical resonant cavity.
(@)
11. W hat are the three important components involved in laser device? (#)
Name the three important components involved in laser device.
(*)
12. How lasers are classified? ( OR) Mention various types of lasers? (*)
13. What are the different modes of vibration of CO
2 and explain any one. (#)
14. Can you mention the function of N
2 and He in CO
2 laser?. (^)
15. What are the two types of transitions possible in a CO
2 laser? (*)
16. What is meant by TEA Laser? (*)
17. Difference between homojunction and heterojunction semiconductor laser.
(^)
Distinguish between homojunction and heterojunction semiconductor laser.
(^)
Compare between homojunction and heterojunction semiconductor laser.
(@)
18. Mention the applications of laser in industry. (*)
Name the applications of laser in industry.
(*)
Explain the applications of laser in industry.
(#)
19. Mention the medical application of laser . (*)
Name the applications of laser in medical (*)
Explain the applications of laser in medical.
(#)
20. Define wave guide . (*)
What is mneant by wave guide? (*)
Explain wave guide.
(#)
21. Explain the principle of optical fibre. (#)
What is the principle behind the optical fiber? (*)
22. What are the conditions for total internal reflection? (#)
Mention the conditions for total internal reflection. (*)
23. Define acceptance angle and numerical aperture. (*) .

Explain acceptance angle and numerical aperture.
(#)
Give explanation for acceptance angle and numerical aperture.
(@)
24. How do you classify the optical fibre? (#)
Classify the optical fiber.
(#)
What are the classification of optical fiber?
(*)
25. What is meant by refractive index profile? (*)
Explain refractive index profile. (#)
26. Differentiate single mode from multimode fibre .
(^)
Distinguish between single mode and multi mode. (^)
Compare single mode and multi mode fiber.
(^)
27. Distinguish between step index and graded index fibre .(^)
Difference between step index and graded index fibre .(^)
Compare step index and graded index fibre .(^)
28. What is meant by attenuation? How will you measure attenuation loss? (*)
Describe attenuation in optical fiber.
(#)
Justify attenuation in optical fiber.
(^)
29. Mention the losses in optical fibre. (*)
30. What is meant by dispersion and mention the different types of it. (*)
Give explanation for dispersion and classify it.
(^)
31. Explain sensors used in optical fiber.(#)
Define sensor. What are the good conditions for sensor? (#)
32. Explain the role of active and passive sensors.
(#)
What is meant by active and passive sensor? (*)
33. Write any 4 major advantages of optical fibre communication. (*)
Describe major advantages of optical fiber communication.
(#)
Mention the advantages of optical fiber communication.
(*)
34. Explain fibre optic endoscope. (#)
What is fibre optic endoscope? (*)
35. Mention the application of optical fibre. (*)
What are the applications of optical febre?
(#)

1.
For atomic transition, derive Einstein’s relations and hence deduce the expressions for the ratio of spontaneous emission rate to the stimulated emission rate. ($) or
(i) Explain spontaneous and stimulated emission of radiation.
(ii)
Discuss the Einstein’s theory of stimulated emission and obtain the expression for the ratio of the spontaneous to stimulated emission coefficients. What are the conclusions drawn from the above expression? (#) or
What is stimulated emission? Explain the existence of stimulated emission using
Einstein’s theory.
(#)
2. Explain different methods of pumping. (#) or
What is pumping action? Explain the methods commonly used for pumping.
(*)
3.
Describe the construction and working of Nd-YAG laser. ($) or
Explain the construction and working of Nd-YAG laser with a neat diagram.List out the applications of this laser. ($) or
Explain the lasing schemes and working of a Nd- YAG laser. (#)
4.
Explain the modes of vibration of CO2 molecule. Describe the construction and working of it. (#) or
What is a molecular gas laser? With neat sketch, explain the construction and working of
CO
2
laser using energy level diagram .(#) or
Describe the construction and working of CO
2
laser and its uses.
5. Describe the construction and working of homojunction and heterojunction semiconductor laser. ($) or
(i) Explain the principle, construction and working of semiconductor diode laser with necessary diagram.
(ii) What are heterojunction lasers? Mention any two advantages of them . (#) or
With a neat diagram explain hoe laser action is achieved in homojunction and hetero junction in Ga – As laser. (^)
6. Explain the industrial applications of laser. (#) or
Discuss the applications of lasers in engineering and industry .(#)
7 . Classify different types of laser based on active medium , with sufficient examples. (#)

8. Explain the principle of optical fibre and hence derive an expression for NA and acceptance angle. (# & ^) or
Define numerical aperture and derive an expression for numerical aperture and angle od acceptance of fiber interms of refractive index of core and cladding .(#) or
(i) Describe propagation of light through an optical fiber.
(ii) What are numerical aperture and acceptance angle? And derive the numerical aperture and acceptance angle. (*)
9. Explain in detail the classification of fibre. (#) or
(i) What is the principle of fiber optics?
(ii) Expplain the various types of optical fibers. (#) or
Classify the optical fibers on the basis of modes of propagation and refractive index profile.
(#) or
9. Write the differences between
a) Step index single mode and multi mode optical fibre. (^)
b) Step index multi mode and graded index multi mode optical fibre. (^)
10. With a neat block diagram explain the fibre optic communication system .(#) or
Explain the functions of different units in fiber optical communication systems with neat block diagram. (#) or
11. Explain the construction and working of displacement and temperature fiber optic sensors.
(#) or
Write a note on fiber optical sensors. (*)
12. Discuss the mechanisms of attenuation, dispersion and bending losses in optical fiber (#) or
Explain in detail the losses in optical fiber .(#)
13. Explain endoscopy in detail with the neat diagram. (#) or
Describe the medical application of fiber optics to view the internal organs of a human body (#)
[ (*) – Remember , (#) – Understand , ($) - Apply , (^) – Analyze , (@) - Evaluate ]