Laser Physics

Course: M.Sc Code: KL-557 Branch: Physics Year: 2023

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Roll No.
Total No. of Questions: 11
[Total No. of Printed Pages : 7]
KL-557
M. Sc. (Sem. IV)
Regular/ATKT/Old ATKT/EX
Examination - May, 2023
PHYSICS
Paper II
Laser Physics
Time : 3 Hours
Maximum Marks : 85
Note : Attempt all questions.
Section A 5×3=15
Objective Type Questions
1.
Choose the correct answer :
(i)
Calculate the wavelength of radiation emitted by an LED made up of a semiconducting material with band gap of energy 2.8 eV :
(a) 2.8 Å
(b) 4.33 Å
(c) 5548.4 Å
(d) 4430.8 Å
(ii)
Which property of a laser is exploited in holography ?
(a) Coherence
(b) Monochromatic
(c) Energetic
(d) Directional
(iii)
The active medium in a Ruby laser taking part in energy exchange process is :
(a) Ruby
(b) Chromium
(c) Neodymium
(d) Calcium
(iv)
One of the schemes to achieve fusion in laboratory is by using :
(a) Sound beam
(b) Gravitational beam
(c) Laser beam
(d) Helium beam
(v)
In harmonic generation process :
(a) integer multiple of frequencies are produced.
(b) integer multiple of amplitude are produced.
(c) integer multiple of directions are produced.
(d) interger multiple of active medium are produced.
Section B 5×5=25
Short Answer Type Questions
2.
Differentiate between spontaneous and stimulated emission processes.
Or
Discuss the properties of an active medium.
3.
Differentiate between temporal and spatial coherence.
Or
Discuss major properteis of laser radiation.
Section C 5×10=50
Long Answer Type Questions
4.
Write a note on semiconductor laser.
Or
Discuss the role played by Ruby in a Ruby laser.
5.
Write a note on Holography.
Or
Give any two applications of Lasers in the field of medicine.
6.
What is Phase Matching Process ?
Or
How does the non-linearity arise in a non-linear medium ?
7.
Derive threshold condition for laser oscillation.
8.
How are the following properties realized in a laser beam ?
(a) Monochromaticity
(b) Coherence
(c) Directionality
Or
Write a detailed note on Einstein's 'A' and 'B' coefficients.
Or
Write a note on various modes of a laser resonator.
9.
Explain the working of a CO₂ laser.
Or
Explain the working of a Nd : YAG laser.
10.
Discuss any two applications of laser from the following :
(a) Hele drilling
(b) Laser welding
(c) Laser cutting
11.
Differentiate between second and third harmonic generation process.
Or
Derive expression for beam width parameter in self focussing of laser beam propagating through a non-linear medium.