Waves and Optics — DU B.Sc. (Hons) Physics Previous Year Question Papers

Maximunn Marks : 75 Q1. Answer any five questions a) What is linearity and supeaposition principle? b) c) d) e) Explain the role of compensating plate in Michelson interferometer. Explain the factors that affect the quality of sound. What are coherent sources? Give examples. Write differences between Fresnel' s and Fraunhofer' s class of diffiaction of light. D Define nodes and antinodes for a stationary wave. g) Distinguish between polarized and unpolarized light. [3x5] a) b) Two collinear sIIMs acting simultaneously on a particle are given by xi= ai sin (®t) x2= a2 sin (cot + dy) where ai and a2 are the amplrfudes of xi and x2, ¢ is the phase difference between the two Find the resultant motion of the particle in terms of ai, a2 and ¢. What are Lissajous figures? Give their applications. a) What are half period zones? Describe the factors on which the amplitude due to a zone b) depends. Using principle of reversibility, show that there is a phase change of 7I when light waves are reflected from the surface of denser medium. [8, 7] a) Derive an expression for the focal length of zone plate. Explain how it acts like a convergent lens having multiple foci. b) Discuss the essential conditions for obtaining a sustained interference pattern. [ 10, 5] a) b) Explain the formation of interference fringes by Fresnel's Biprism when a monochromatic soul.ce of light is used. Derive the expression for ffinge width. Two narrow parallel slits o.5 X 10-3 in apart are illuminated by amonochromatic ligiv of wavelength 5890 A. Calculate the width of fringes which are obtained on a screen distant 0.5 in from the slits. [10,5] a) What areNewton's rings? Howthey are constructed. Show that in reflected licht b) diameters of bright rings are proportional to square root of odd natural numbers and diameters of dark rings are proportional to square root of natural numbers. Explain the phase velocity and group velocity. [12, 3] a) b) Describe Fraunhofer diffraction by a single slit using a well labelled diagram. Also draw the intensity diagram. What is a plane polarised light. Discuss the method for the production of plane polarised light. [9, 6]