Search, filter, and study UPSC Civil Services & IFoS Physics past year questions with rigorous derivations, formulas, and step-by-step solutions.
An observer S_1 sees two bodies A and B having equal rest mass approach each other with equal but opposite velocities 4c/5. To a second observe S_2, the body A is at rest. What us the velocity of the body B as seen by observe S_2? What are the kinetic energies of the body B in the frames of S_1 and S_2?
A block of mass m, attached to an ideal massless spring of force constant k, is at rest on a smooth horizontal floor. A second block of mass 2 m, moving with an initial velocity strikes the free end of the spring. The collision is one dimensional and elastic. (i) Calculate the maximum compression of the spring. (ii) What are the velocities of the block long time after the collision?
Write the Euler's equations for the rotational motion of a rigid body with one point fixed, under the action of torque N. Apply these equations to discuss the rotational motion of a symmetrical top in the absence of any force other than the reaction at the fixed point.
What are the main applications of JFET? Discuss their advantages over bipolar transistors. Explain the working of n-channel JFET with the help of a schematic diagram.
(i) Show that a negative logic OR gate is like a positive logic AND gate. (ii) Distinguish between Hadrons and Leptons.
(i) Discuss the variation of free carrier concentration with temperature for an intrinsic and extrinsic semiconductors. (ii) Explain the effect of negative and positive voltage feedback on an amplifier characteristics.
Write down the characteristics of an ideal operational amplifier. Explain the term virtual ground. Draw a circuit diagram showing virtual ground in an operational amplifier.
Explain Meissner effect and Josephson effect. Describe their applications in the field of superconductivity.
(i) What is the lowest non zero angular momentum for an elementary particle? Name at least three elementary particles having such an angular momentum. (ii) Write the spectral symbol of the term with S= 1/2, J = 5/2 and g = 6/7.
Mention the conservation laws for strong, electromagnetic, and weak interactions.
Which conservation laws are obeyed in nuclear reactions? Explain the significance of Q value of a nuclear reaction.
(i) Explain why a neutral particle such as neutron possesses a finite value of magnetic moment, and how it is determined. (ii) Write down the electronic configuration of ^7\text{Li}, \, ^{13}\text{C} \quad \text{and} \quad ^{25}\text{Mg} in the ground state of the nuclear shell model.
]-decay of radioactive nuclei. (ii) Show that for a cubic lattice, the difference between the successive h, k, l planes is given by d_{h,k,l} = \frac{a}{\sqrt{h^2 + k^2 + l^2}}
Explain shell model of the nucleus. Give evidence for nuclear shell structure. What are the limitations of the shell model?
Distinguish between particle and antiparticle. How antiparticles were discovered?
Derive an expression for the spin-orbit interaction energy in one electron system. Calculate the energy separation between the levels ^2P_{1/2} and ^2P_{3/2}.
Write the electronic configuration of mercury (Z = 80). Obtain the spectral term for the normal and the first excited configuration of the atom.
A diatomic gas is found to have a number of absorption bands in the ultraviolet region. Each band is also observed to have a fine structure. How can the observed spectrum be explained and analyzed?
Explain the nature, origin and significance of 21 cm hydrogen line.
Calculate the change in rotational constant (B_v) when deuterium is substituted for hydrogen in a hydrogen molecule.