UPSC Physics Optional PYQs (CSE & IFoS)PYQs

What is stimulated emission of light? How does it differ from spontaneous emission? Name any device basal on the stimulated emission of light and explain its working.

Write a note on Uses of multiple beam interferometry.

How can one produce (i) left-handed circular motion, and (ii) right-handed circular motion by combining two simple harmonic motions? Justify, your answers.

Define and explain the terms resolving power and magnifying power of an optical instrument. For a telescope, on that parameter do these depend? For a given resolving power, what is the optimum magnifying power?

Parallel light is incident normally on diffraction grating having 6,000 lines per cm. Find the angular separation between the maxima for wavelengths 5,890 Å and 5,896 Å in the second order.

Using Huyghens' construction, discuss the propagation of O and E waves in a biaxial crystal when the optic axis is perpendicular to the plane of incidence and parallel to the boundary surface. Take the incident ray to be oblique.

Out of the following three functions only one can be Fourier analysed in the range -\pi \leqslant x \leqslant \pi. Choose the correct function and obtain its Fourier series expansion: (i) f(x) = x^{2} \text{ for } 0 < x < \pi (ii) f(x) = 0 \text{ for } -\pi < x < 0 = \pi \text{ for } 0 < x < \pi (iii) f(x) = 1/x^{2} \text{ for } -\pi < x < \pi

The angular frequency, \omega, of a wave is related to the wave vector, k, by the relation \omega = \omega_{0} \sin\frac{ka}{2} \text{ for } 0 < k > \frac{\pi}{a} Determine the phase and group velocities of this wave and draw a rough sketch to show their variation with k(0 < k < \pi/a)

Water is observed to flow through a capillary of diameter 1.0\text{ mm} with a speed of 3\text{ ms}^{-1} viscosity of water in c.g.s. units is : 0.018 at 0^{\circ}\text{C} 0.008 at 30^{\circ}\text{C} 0.004 at 70^{\circ}\text{C} Calculate he Reynolds numbers, and test at which of these three temperatures is the flow likely to be streamlined.

Calculate the velocity of an electron having kinetic energy 1 MeV.

Write a note on Bernoulli's theorem and its applications.

A solid sphere of mass 6\text{ kg}, diameter 20\text{ cm}, and uniform density rolls over a surface with a speed of 2\text{ ms}^{-1}. Calculate its kinetic energy.

Explain clearly why Young's modules Y of a material determines the resistance to bending of a thin rod made of that material. Derive the expression for the work done when a wire of length l and cross-sectional area A is stretched by an amount x(\le l) under a given load corresponding to equilibrium at stretching x.

Calculate the mass of the Sun, given the distance of the Earth from the sun to be 1.5 \times 10^{8}\text{ km}.

n identical drops of water, each of radius r_{2}, coalesce to form a large drop of radius R. Calculate the energy released in the process and the consequent rise in temperature of water.

A rocket is fired vertically up. During the burning of the engine, which lasts for 50\text{ s}, a constant acceleration of 2.0\text{ g} is observed. What is the speed of the rocket at the end of 50\text{ s}? Calculate the maximum height to which the rocket will rise before it begins to fall back. Take = g = 9.80\text{ ms}^{-2} and neglect the variation of g with height.

A neutron having kinetic energy E collides head on with a {}_{6}^{12}\text{C} nucleus and rebounds perfectly elastically in the direction from which it came. Determine the kinetic energy of the neutron after collision.

The earth receives from the Sun 1.37\times 10^{3}\text{ W/m}^{2} of power on the top of the atmosphere. Calculate the mass of the Sun that is converted into energy in one second.

The orbit of the earth is an ellipse wite eccentricity 0.0167. Determine the ratio of the maximum speed of the earth to its minimum speed.

Give the basic structure of a n-channel depletion type MOSFET. Draw the drain current-drain voltage characteristics both in depletion as well as in enhancement modes.