UPSC Physics Optional PYQs (CSE & IFoS)PYQs

What are magic numbers? Discuss shell structure of a nucleus. How is this model able to explain various properties of nuclei? Discuss the limitations of this model.

Predict from the single particle shell model the shell configuration, ground state spin and parity for the following nuclei: {}^{13}_{7}\mathrm{N};\ {}^{17}_{8}\mathrm{O}

Explain parity violation in \beta-decay. Describe how parity violation was experimentally detected in the decay of {}^{60}\mathrm{Co}.

Calculate the packing fraction and the binding energy per nucleon for {}^{16}_{8}\mathrm{O} and {}^{87}_{38}\mathrm{Sr} nuclei.

A star converts all its hydrogen to helium, achieving 100% helium. It then converts the helium to carbon via the reaction {}^{4}_{2}\mathrm{He}+{}^{4}_{2}\mathrm{He}+{}^{4}_{2}\mathrm{He}\rightarrow{}^{12}_{6}\mathrm{C}+7\cdot27\mathrm{MeV} The mass of the star is 5.0\times10^{32}\,\mathrm{kg} and it generates energy at the rate of 5\times10^{30}\,\mathrm{W}. How long will it take to convert all Helium to carbon at this rate?

In \mathrm{CO} molecule J = 0 \to J = 1 line occurs at a frequency 1.153 \times 10^{11}\ \mathrm{Hz}. Calculate the moment of inertia of \mathrm{CO} molecule.

What is Raman Effect? How does it differ from Rayleigh scattering? Explain Raman Effect on the basis of quantum mechanical theory. How is Raman Effect experimentally studied? What are the advantages of using laser sources in the study of Raman Effect?

Is it possible to obtain pure rotational spectra of \mathrm{H}_2, \mathrm{HF}, \mathrm{O}_2 and \mathrm{NO} molecules?

State and explain Franck-Condon principle. Discuss its applications in molecular spectroscopy.

Discuss occurrence of rotational energy levels of a diatomic molecule and show that the pure rotation spectrum of such a molecule consists of a series of equally spaced lines separated by a constant wave number difference 2B. Write down the selection rules.

What is Zeeman effect? How it can be understood on quantum mechanical basis? Obtain an expression for Zeeman splitting of atomic energy levels in a magnetic field B. Explain the magnetic splitting of sodium D-lines.

What is spin-orbit interaction? Calculate the energy shift due to spin-orbit interaction term in H-like system. Discuss the significance of this shift in relation to the fine structure of hydrogen spectral lines.

A stream of particles of mass M and energy E is directed from left to a one-dimensional potential barrier as shown in the above figure. Set up the time-independent Schrodinger equation and obtain an expression for transmission probability from region I to II. How this phenomenon helps in the understanding of \alpha-decay of nuclei?

Show that the Pauli spin matrices satisfy the following: \sigma_x^2=\sigma_y^2=\sigma_z^2=1 \sigma_x\sigma_y=-\sigma_y\sigma_x=i\sigma_z \sigma_y\sigma_z=-\sigma_z\sigma_y=i\sigma_x \sigma_z\sigma_x=-\sigma_x\sigma_z=i\sigma_y

A system is described by the Hamiltonian operator, H=-\dfrac{d^2}{dx^2}+x^2. Show that the function A x\exp\left(-\dfrac{x^2}{2}\right) is an eigen function of H. Determine the eigen values of H.

The normalized wave function for the electron in hydrogen atom for the ground state is \psi(r)=(\pi a_0^3)^{-1/2}\exp\left(-\frac{r}{a_0}\right) Where a_0 is the radius of the first Bohr orbit. Show that the most probable position of the electron is a_0.

Derive Bohr's angular momentum quantization condition in Bohr's atomic model from the concept of de Broglie waves.

Calculate the change in pressure for a change in freezing point of water equal to -0.91^\circ\mathrm{C}. Given, the increase of specific volume when 1 gm of water freezes into ice is 0.091 cc/gm and latent heat of fusion of ice is 80 cal/gm.

Derive an expression for the thermal efficiency of a reversible heat engine operating on the Diesel cycle with an ideal gas of constant heat capacity as the working medium.

1 kmol of an ideal gas is compressed isothermally at 400 K from 100 kPa to 1000 kPa in a piston and cylinder arrangement. Calculate the entropy change of the gas, the entropy change of the surroundings and the total entropy change resulting from the process if the process is mechanically reversible and the surroundings consist of a heat reservoir at 400 K.