DAW-January

Lasers-Einstein A and B coefficients;Ruby and He-Ne lasers; Characteristics of laser light-spatial and temporal coherence; Focusing of laser beams; Three-level scheme for laser operation; Holography and simple applications. Questions: Q 1. In He-Ne laser, what is the function of He gas? Explain the answer with the help of energy level diagram for He-Ne laser ? […]

Production and detection of linearly and circularly polarized light; Double refraction, quarter wave plate; Optical activity; Principles of fibre optics, attenuation; Pulse dispersion in step index and parabolic index fibres; Material dispersion, single mode fibres; Questions: Q 1. For a multimode step-index optical fibre, the core refractive index is 1.5 and the fractional index difference

Fresnel diffraction: half-period zones and zone plates, circular aperture. Questions: Q 1. Show that the areas of all the half-period zones are nearly the same. Find the radius of 1st half-period zone in a zone plate whose focal length is 50 cm and the wavelength of the incident light is 500 nm. [15 marks] Q

Fraunhofer diffraction-single slit, double slit, diffraction grating, resolving power; Diffraction by a circular aperture and the Airy pattern; Questions: Q 1. Can D1 and D2 lines of sodium light be resolved in second-order spectrum if the number of lines in the given grating is 450? Explain.   λD1=5890A0\lambda_{D1}=5890 A^0λD1​=5890A0 and  λD1=5890A0\lambda_{D1}=5890 A^0λD1​=5890A0. [10 marks] Q

Michelson interferometer; Multiple beam interference and Fabry-Perot interferometer. Questions: Q 1. Describe how Michelson Interferometer can be used to determine refractive index of a gas. In a Michelson Interference experiment, a tube of length 25 cm containing a gas of refractive index μ\muμ  is introduced between the upper mirror and the beam splitter. 150 fringes

Interference of light-Young’s experiment, Newton’s rings, interference by thin films, Questions: Q 1. What are Newton’s rings? How are they formed by two curved surfaces ? [10 marks] Q 2. A soap-film of refractive index 1.33 is illuminated with light of different wavelengths at an angle of 45°45\degree45°. There is complete destructive interference for λ\lambdaλ

nodal planes, system of two thin lenses, chromatic and spherical aberrations. Questions: Q 1. A thin converging lens and a thin diverging lens are placed coaxially at a distance of 5 cm. If the focal Length of each lens is 10 cm, find for the combination (i) the focal length (ii) the power (iii) the

Laws of reflection and refraction from Fermat’s principle; Matrix method in paraxial optics-thin lens formula, Questions: Q 1. State and explain the Fermat’s principle of extremum path. Discuss the cases of rectilinear propagation of light and reversibility of light rays in the context of Fermat’s principle. Using Fermat’s principle, deduce thin lens formula. [15 marks]

Simple Beats; Stationary waves in a string; Pulses and wave packets; Phase and group velocities; Reflection and Refraction from Huygens’ principle. motion, damped oscillation, forced oscillation and resonance; Questions: Q 1. An observer on a railway platform observed that as a train passed through the station at 108 km/hr, the frequency of the whistle appeared

Simple harmonic motion, damped oscillation, forced oscillation and resonance; Questions: Q 1. During an earthquake, a horizontal shelf moves vertically. If its motion can be regarded as simple harmonic motion, calculate the maximum value of amplitude of oscillation so that the books resting on it stay in contact with it always. Take   g=9.9 m/s2g=9.9\ m/s^2g=9.9 m/s2