UPSC Physics Optional PYQs (CSE & IFoS)PYQs

Explain the salient features of fluorescence and phosphorescence with the help of energy level diagram. Name a few applications of these phenomena in our daily life.

Distinguish between fluorescence and phosphorescence. Explain the mechanisms responsible for these phenomena. Discuss the applications of fluorescence and phosphorescence in the fields such as biochemistry, material science, etc.

If {}^{11}\text{Na} atoms in their ground state are placed in a region having electromagnetic radiation of frequency \nu = 1\cdot 0 \times 10^{10}\text{ Hz}, calculate the required magnetic field B at which the electromagnetic radiation will be in resonance with the Zeeman splitting.

Write the electronic configurations for carbon (C), nitrogen (N) and oxygen (O) atoms, and then derive their ground states.

Draw the normal Zeeman pattern for {}^1\text{F}_3 - {}^1\text{D}_2 transition.

The force constant of \text{HCl} molecule is 4\cdot 8 \times 10^5 \text{ dyne/cm}. Calculate the wave numbers of Stokes and anti-Stokes lines, when excited with a radiation of wavelength 4358 \text{ \AA}. [ Given, \mu_{\text{HCl}} = 1\cdot 61 \times 10^{-24} \text{ g} ]

(i) Discuss the importance of studying the isotope effect in rotational spectroscopy. (ii) If hydrogen is substituted by deuterium in hydrogen molecule, calculate the change in rotational constant B.

In case of pure rotational states, if the temperature will be doubled, then calculate the rotational quantum number corresponding to maximum population density. [ Assume that temperature is high ]

What is Lamb shift in the fine structure of hydrogen spectrum ? Discuss its theory based upon second quantization.

Explain how the hydrogen spectrum is used for imaging the universe.

Describe Electron Paramagnetic Resonance. Highlight its differences with NMR and discuss its applications.

Show that for a diatomic molecule with two nuclei of mass 'M' separated by a distance 'a', the rotational energy of nuclear motion is lower than electronic energy by a factor of \frac{m_e}{M}.

Explain the formation of molecular hydrogen in the interstellar medium.

How do Stokes lines appear in Raman spectrum as per classical and quantum theory of Raman effect ?

The force constant of the bond in CO molecule is 1900\text{ N m}^{-1}. Calculate the energy of the lowest vibrational level. The reduced mass of CO molecule is 1\cdot 14 \times 10^{-26}\text{ kg}. Given h = 6\cdot 63 \times 10^{-34}\text{ J s} and 1\text{ eV} = 1\cdot 6 \times 10^{-19}\text{ J}.

Calculate the possible angles between \vec{L} and \vec{S} for a d-electron in one-electron atom.

A beam of hydrogen atoms in a Stern-Gerlach experiment obtained from an oven heated to a temperature of 400\text{ K} passes through a magnetic field of length 1\text{ m} and having a gradient of 10\text{ T/m} perpendicular to the beam. Calculate the transverse deflection of an atom of the beam at a point where the beam leaves the field. The value of Bohr magneton \mu_B is 9\cdot 27 \times 10^{-24}\text{ A m}^2 and the Boltzmann constant k is 1\cdot 38 \times 10^{-23}\text{ J/K}.

Differentiate between L-S coupling and J-J coupling. What are the possible orientations of \vec{J} for the J = \frac{3}{2} and J = \frac{1}{2} states that correspond to l = 1 ?

How is Rydberg constant related to emission wavelength of hydrogen spectrum ?

Describe in brief the Raman effect.