UPSC Physics Optional PYQs (CSE & IFoS)PYQs

What is X-ray diffraction? How is an XRD pattern used to determine the crystal structure of the material?

Classify diamagnetic, paramagnetic and ferromagnetic materials in terms of their magnetic susceptibility (\chi). Plot and explain the variation of \frac{1}{\chi} with temperature for the three materials.

(i) Explain the Bravais lattice and non-Bravais lattice with suitable diagram. (ii) Draw the (1\ 0\ 0), (1\ 1\ 0) and (1\ 1\ 1) planes in a cubic unit cell. (iii) Obtain the Miller indices of a plane with intercepts a, b/2, 3c in a simple cubic unit cell.

Consider an energy band which is filled with electrons up to a certain value k_1 \left(k_1 < \frac{\pi}{a}\right). Determine the total effective number of free electrons in the energy band. Comment on the electron distribution in an insulator, intrinsic semiconductor and metals at 0\text{ K}. Symbols have their usual meanings.

What are the differences in electrical characteristics of FET (JFET) and MOSFET?

What is an oscillator? Explain the Barkhausen criterion and working principle of an R-C phase-shift oscillator with suitable circuit diagram.

What is a microprocessor? Briefly mention the basic units of a microprocessor by drawing descriptive block diagram of 8085 microprocessor.

How does n-channel FET differ from p-channel FET?

What is a microprocessor? Describe the internal functioning of a microprocessor with block diagrams.

(i) How will you obtain OR gate from NAND gate? Draw the logic circuit for the following expressions : Y = ABC + \bar{D} Y = (\bar{E}G + B)H (ii) What is a thermistor? Explain the working of thermistor by drawing temperature-resistance curve.

What is the minimum energy required to break a {}_2^4\text{He} nucleus into free protons and neutrons? [ Given, m_{\text{H}} = 1\cdot 007825 \text{ amu}, m_n = 1\cdot 008665 \text{ amu}, m_e = 0\cdot 00055 \text{ amu} and m_{\text{He}} = 4\cdot 002603 \text{ amu} ]

Consider a uranium nucleus ({}_{92}\text{U}^{236}) breaking up spontaneously into two equal parts. Estimate the reduction of electrostatic energy of the nucleus considering uniform charge distribution. [ Assume that nuclear radius is 1\cdot 2 \times 10^{-13} A^{1/3} \text{ cm} ]

State the basic assumption of single-particle shell model. How do the centrifugal and spin-orbit terms remove the degeneracy of three-dimensional spherical harmonic oscillator?

\rho^0 and \text{K}^0 mesons both decay mostly to \pi^+ and \pi^-. Why the mean lifetime of \rho^0 is 10^{-23} \text{ s}, whereas that of \text{K}^0 is 0\cdot 89 \times 10^{-10} \text{ s}?

If plutonium ({}^{239}_{94}\text{Pu}) is used as fuel in a fission reactor and is producing fragments barium ({}^{146}_{56}\text{Ba}) and strontium ({}^{91}_{38}\text{Sr}) by initiating the reaction by one neutron and producing three neutrons in the process, then calculate the number of fissions per second required in a 100\text{ MW} reactor. [Given : BE per nucleon (MeV) : 7\cdot 6 for {}^{239}\text{Pu}, 8\cdot 2 for {}^{146}\text{Ba} and 8\cdot 6 for {}^{91}\text{Sr}]

By considering a suitable nuclear potential well for the deuteron ground state, show that it is a loosely bound nucleus.

What do you understand by \text{SU}(3) symmetry for the quark model? On the basis of it, explain that the baryons can have +2 charge but mesons cannot have the same.

The total binding energies of {}_8^{15}\text{O}, {}_8^{16}\text{O} and {}_8^{17}\text{O} are 111\cdot 96 \text{ MeV}, 127\cdot 62 \text{ MeV} and 131\cdot 76 \text{ MeV} respectively. Determine the energy gap between 1p_{1/2} and 1d_{5/2} neutron shells for the nuclide whose mass number is close to 16.

(i) \pi^- \rightarrow \mu^- + \bar{\nu}_\tau (ii) n \rightarrow p^+ + e^- + \bar{\nu}_e Explain the various leptonic family members. What is leptonic number conservation? Based on this conservation law, tell whether the following reactions are possible or not : (i) \pi^- \rightarrow \mu^- + \bar{\nu}_\tau (ii) n \rightarrow p^+ + e^- + \bar{\nu}_e

Calculate the minimum energy (E_\gamma) required for a gamma ray photon to disintegrate a deuteron of mass M and binding energy B into a neutron and a proton. (Assume B \ll Mc^2)