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Friday, 28 March 2014

Optics-Model question paper for Msc

1(a) Why light is categorized in the category of electromagnetic waves? (4 Marks)
(b) State and explain Fermat's principle of extremum path and use it to deduce the laws of reflection and refraction of light. (6 Marks)
(c) What do you understand by the power of a lens? Calculate the power of two thin lenses of focal length f1 and f2 separated by a distance d. (6 Marks)
(d) A glass dumbbell of length one meter and refractive index 1.5 has ends of radius of curvature 5 cm. Calculate the position of the image due to reflection at one end only, when the object is at a distance of 40 cm from one end. (4 Marks)
2(a) Define cardinal points of a system of co-axial lenses. Describe how you would determine experimentally the principal planes of a combination of two thin lenses separated by a distance. (6 Marks)
(b) Describe nodal assembly methods to locate cardinal points of a lens system experimentally. Explain its working with particular reference to the characteristics of nodal points. (6 Marks)
(c) What is the advantage of using matrix method in paraxial optics? (4 Marks)
(d) The focal length of each lens of Ramsden's eyepiece is 4 cm by matrix formulation. Find the focal length and determine the positions of the cardinal points. (4 Marks)
3(a) Derive the condition for the combination of two thin prisms to produce mean deviation without net dispersion. Derive an expression for the net mean deviation. (6 Marks)
(b) Enumerate the various defects of image formation by an optical system. Explain the methods of removing them. (4 Marks)
(c) Explain the terms entrance pupil and exit pupil. (6 Marks)
(d) Light travels to a target and back in 0.5 sec in carbon disulphide. Calculate the distance of the target if the refractive index of the carbon disulphide is 1.46. (4 Marks)
4(a) What is the difference between oscilatory motion and wave motion? (4 Marks)
(b) What is normal and anomalous dispersion? Derive Sellmeier's equation for the refractive index of a dielectric medium. (6 Marks)
(c) Prove Snell's law of reflection and refraction taking the oblique incidence of elctromagnetic wave on an interference between two dielectric media. (6 Marks)
(d) Find the velocity of a plane wave in a loss less medium having a relative permittivity of 5 and relative permeability of 1. (4 Marks)
5(a) What are coherent sources? How are they realized in practice? Describe a method for determining the refractive index of a gas using the interference phenomena. (8 Marks)
(b) What are the conditions for sustained interference pattern? (4 Marks)
(c) What will happen if wedge shaped film is placed in white light? (4 Marks)
(d) In a Newton's rings experiment, the diameter of 10th ring changes from 1.4 to 1.27 cm when a drop of liquid is introduced between the lens and the glass plate. Calculate the refractive index of the liquid. (4 Marks)
6 (a) Explain the construction of Fresnel's half period zones. (6 Marks)
(b) Give the theory of diffraction grating. Describe in detail how you would use a transmission grating for measuring the wavelength of light. (6 Marks)
(c) Discus Fraunhofer diffraction pattern of a straight edge. (4 Marks)
(d) An optical filter has a line width of 1.5 nm and mean wavelength 550 nm. With white light incident on the filter, calculate (i) coherent length and (ii) the number of wavelengths in the wave train. (4 Marks)
7 (a) Explain Rayleigh criterion for resolution and discuss it in relation to the resolving power of a microscope. (6 Marks)
(b) What is meant by optical rotation? State any two laws of optical rotation. (6 Marks)
(c) State and explain the law of Malus. (4 Marks)
(d) Calculate the thickness of a double refracting plate capable of producing a path difference of λ/4 between extra ordinary and ordinary waves. Given μo= 1.53 μe = 1.54 and λ = 5890Å. (4 Marks)
8(a) Explain some important properties of hologram. (4 Marks)
(b) Describe various mechanisms of dispersion in optical fibers. Explain the effect of dispersion on the bandwidth of optical communication channel. (6 Marks)
(c)Explain stimulated Raman scattering. How can it be explained using quantum concept? (6 Marks)
(d)At what temperature are the rates of spontaneous and stimulated emission equal? Assume λ = 5000Å. (4 Marks)

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