UPSC Physics Optional PYQs (CSE & IFoS)PYQs

What are the different methods used to increase the probability of exposure for the atomic planes with right orientation to X-rays in the X-rays diffraction studies?

Discuss the Debye model of lattice specific heat. What are the limitations of the Debye model?

The input signal as shown in Figure (I) is applied to the comparator circuit given in Figure (II). Make a sketch of the output signal showing its proper relationship to the input signal. Assume that the maximum output levels of the op-amp are \pm 12\text{ V}.

Draw a diagram of magnetic susceptibility as a function of temperature. Pay attention to the relative scales in your diagram so that the relative strengths of the magnetic phenomena are presented.

What are the physical reasons that the effective mass of an electron can be infinite and negative?

The energy near the valence band edge of a crystal is given by E = -10^{-39} k^2\text{ J}\cdot\text{m}^2. An electron with wave vector 10^{10}\hat{k}_x\text{ m}^{-1} is removed from an orbital in the completely filled valence band. Determine its effective mass and momentum.

What is diamagnetism? Why do diamagnetic materials have negative magnetic susceptibility?

Explain the principle and working of the Laue's diffraction method. Comment on the origin of Laue spots and the utility of Laue's diffraction pattern.

Discuss the limitations of the quantum theory of diamagnetism.

What is the effective mass of an electron?

What is the photovoltaic effect? What are the processes that are required to obtain a useful power output from photon interactions in a semiconductor? List the factors that affect the efficiency of a solar cell.

Explain briefly the two-fluid model proposed by the London brothers and obtain the expressions for the penetration depth and the number of superelectrons in a superconducting specimen.

At very low temperatures, the specific heat of rock salt varies with temperature according to the Debye T^3 law. The Debye temperature for rock salt is 281\text{ K}. How much heat will be required to raise the temperature of 2\text{ kilo-mol} of rock salt from 10\text{ K} to 50\text{ K}?

What is the criticality of a self-sustained nuclear reactor? Write the basic processes affecting the nuclear chain reactions of a finite-size nuclear reactor. Also, write the critical size of reactors of different shapes in terms of geometrical buckling constant.

By considering the three-dimensional harmonic oscillator potential, explain the energy levels of nucleons inside the nucleus. Also, derive the zero-point energy of nucleons. Why did this assumption fail to explain the existence of nuclei with higher magic number?

What do you understand by the packing fraction 'f' and the binding energy 'E_b' of a nucleus? Draw the graphs for packing fraction f versus mass number (A) and binding energy fraction f_b \left(= \dfrac{E_b}{A}\right) versus mass number (A). Further, explain how the graphs of the variation of f and f_b with A have complementary approaches.

What do you understand by the \text{SU}(3) symmetry for the classification of baryons and mesons? Draw the octets for baryons and mesons along with their quarks and antiquarks.

Are the nucleons inside the nucleus governed by the laws of quantum physics? Justify your answer.

Binding energy and rest mass energy of a two-nucleon bound state are denoted by B and Mc^2, respectively, where c is the speed of light. Calculate the minimum energy of a photon required to dissociate this bound state in terms of B and Mc^2.

A nucleus of rest mass M is initially in an excited state whose energy is \Delta E above its ground state. The nucleus emits a \gamma-ray of energy h\nu and makes a transition to its ground state. Calculate the fractional change in energy for the nucleus.