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IGNOU: Optics : PHE-09 December, 2017 Solved Question Paper
Note: All questions are compulsory but there are internal choices. The marks for each question are indicated against it. You can use log tables or a calculator. Symbols have their usual meanings.
Q1. Attempt any five parts:
(a) Briefly describe myopia, hypermetropia and astigmatism defects of vision.
Ans. Refer to Chapter-3, 3.1 HERE
(b) What is double refraction or birefringence? Draw o-and e-wave surfaces for a negative uniaxial crystal.
Ans. Refer to Chapter-4, 4.3 HERE
(c) Two light waves of the same frequency and constant phase difference have intensities in the ratio 81: 1. When these waves are superposed, they produce interference fringes. Calculate the ratio of the maximum to minimum intensity.
Ans. Same as Chapter-5, Q.No.-2 HERE
(d) Define temporal and spatial coherence.
Ans. Refer to Chapter-12, 12.2 and 12.3 HERE
(e) Green light of wavelength 5100 from a narrow slit is incident on a double slit. If the overall seperation of 10 fringes on a screen 2 m away is 2.0 cm, calculate the double slit seperation.
Ans. HERE YOU GET FULL ANSWER HERE
(f) Draw energy level diagram of a Helium-Neon Laser.
Ans. Refer to Chapter-13, 13.3 HERE
(g) Discuss the spatial evolution of diffraction pattern from Fresnel to Fraunhofer class.
Ans. Refer to Chapter-8, 8.2 HERE
(h) A coin has a diameter of 3 cm. How many Fresnel zones does it cut off if the screen is 2 m away? Do you expect to see a bright spot at the centre? Take
Ans. Same as Chapter-8, Q.No.-5 HERE
Q2. Using Maxwell’s equations in vacuum, derive wave equations for electric field, of an electromagnetic wave. Show that the speed of propagation of an electromagnetic wave in free space is given by
Ans. Refer to Chapter-1, 1.3 HERE
Or
What do you mean by polarisation of light? Two orthogonal linearly polarised lights with instantaneous electric field vectors having phase difference are superposed. Show that the resultant is an elliptically polarised light.
Ans.Now, Refer to Chapter-4, Q.No.-1 HERE
Q3. (a) Discuss the use of Michelson interferometer for the determination of refractive index of a thin plate.
Ans. Refer to Chapter-7, 7.2 HERE
Or
With the help of a diagram, explain the formation of fringes by Lloyd’s single mirror.
Ans. Refer to Chapter-5, 5.7 HERE
(b) Write Stoke’s relations. A parallel beam of sodium light is incident on a thin glass plate such that the angle of refraction into the plate is 60°. Calculate the smallest thickness of the glass plate which will make it appear dark by reflection.
Ans. Refer to Chapter-6, 6.1 and Q.No.-3 HERE
Or
In Young’s double slit experiment, the slits are 0.2 mm apart. An interference pattern is observed on a screen 0.5 m away. If the wavelength of the light used is 5000 calculate the distance between the central maxima and the third minima on the screen. If one of the slits is covered by mica sheet of thickness cm, calculate the shift in the central fringe. Take refractive index of mica as 1.58.
Ans. Refer to Chapter-5, Q.No.-14 HERE
Q4. Attempt any two parts:
(a) What are half-period zones? Show that they are of equal area.
Ans. Refer to Chapter-8, 8.3 HERE
(b) What do you understand by the resolving power of an optical instrument? Obtain an expression for the resolving power of a microscope.
Ans. Refer to Chapter-11, 11.2 HERE
(c) A diffraction limited laser beam of diameter 5 mm is directed at the earth from a space laboratory at an altitude of 600 km. How large an area would the central beam illuminate?
Ans. Same as Chapter-11, Q.No.-7 HERE
Q5. Attempt any two parts:
(a) With the help of an appropriate diagram, discuss the production of a hologram. List two practical considerations in the productions of a hologram.
Ans. Refer to Chapter-14, 14.3 HERE
(b) Briefly describe the applications of lasers in the fields of communication and medicine.
Ans. Refer to Chapter-13, 13.4 HERE
(c) Discuss the role of core and cladding in optical fibres. Draw the labelled refractive index profiles for step-index and gradient-index fibres.
Ans. Refer to Chapter-15, 15.1 HERE