JUNE-2021
B. Sc. (IV Semester) Examination
PHYSICS
Paper: PHY-241 (New Course)
(Physical Optics and Modern Physics)
Full Marks : 60
Pass Marks : 35%
Time : Two Hours
Note: 1. In Section A any three questions are to be answered. In Section B any three questions are to be answered.
2. The figures in the margin indicate full marks for the questions.
Section – A
(Physical Optics)
1. (a) Show ray diagram how a biprism produces coherent sources. Derive expression for fringe width of interference pattern produced by a biprism. 7
(b) Find the condition for constructive and destructive interference. 3
2. (a) Discuss interference produced by wedge shaped film. What is the nature of the fringe pattern. 5
(b) How wavelength of light is determined by Newton’s ring. 5
3. (a) Distinguish between Fresnel and Fraunhofer diffraction. 2
b) Discuss the difference in a single slit. Find out expression for intensity variation in the diffraction patterns. 8
4. (a) Describe the theory of transmission grating. How wavelength of light can be determined by using a grating. 7
(b) What is population inversion and how it can be possible? 3
5. Write short not on any two: (5x2= 10)
(a) Zone plate
(b) Michelson interferometer
(c) Retarding plate
Section – B
(Modern Physics)
6. (a) Write the properties of positive rays. 3
(b) Describe Thomson experiment to determine e/m of electron. 7
7. Describe Rutherford alpha scattering
(a) Experiment of discuss the Rutherford atomic model. 7
(b) Write the limitation of Rutherford model and how it could be solved by Bohr. 3
8. Discuss how the binding energy –
(a) Graph could predict about the nature of nuclear force. What other important conclusions were drawn from this graph. 6
(b) State and explain Geiger-Nuttal Law. 4
9. (a) Write the principle, construction and working of nuclear reactor. 6
(b) Discuss different types of beta decay and their mechanism. 4
10. Write short note of any two (5x2=10)
(a) Aston mass spectrograph
(b) Neutron Theory
(c) Frank-Hertz experiment
