UPSC Physics Optional PYQs (CSE & IFoS)PYQs

Write a short note on Stellar spectra.

Calculate the bond length and force constant of the bond of {}^{12}\text{C}\ {}^{16}\text{O} molecule; given 0 \rightarrow 1 rotational line in v = 0 state is at 115.3\text{ GHz} and the wavelength of the vibrational frequency is 14.7\ \mu\text{m}.

Describe Frank Hertz experiment to establish the quantization of energy levels.

What is space quantisation? Discuss the Stern Gerlach experiment establishing the space quantisation.

Explain the orgin of anti-Stokes lines in Raman spectra.

What are the term symbols of 2 equivalent p electrons? Write down the term symbols in ascending order of energies.

Describe briefly how it is possible to determine the elements present at the surface of a given star.

Discuss the gross and fine structure of electronic band spectra of a diatomic molecule.

Give the theory of vibration-rotation spectra of diatomic molecules. Explain the nature of P, Q, R branches.

A sample shows a Raman line at 4200\text{ \AA}, with incident radiation having \lambda = 4400\text{ \AA}. Where Will the other corresponding Ramas line fall with the same exciting radiation? Will that line be stronger or weaker than the line at 4200\text{ \AA}, and why?

Give the salient features of electronic band spectra of diatomic molecules in emission. Why would absorption, spectra of the same molecules be simpler? The absorption spectrum of iodine (\text{I}_2) vapour has longest wavelength band at \lambda_0, initial band separation \Delta\lambda_0, and bands converge at wavelength \lambda_0'. Relate these data broadly to the concerned parameters of \text{I}_2 molecule.

Write a short note on Pauli's exclusion principle and its application.

Raman effect differs from Rayleigh scattering Explain. Explain qualitatively how Raman lines originate. What is the difference between Raman scattering and compton scattering?

Give the quantum numbers of the states whose energy difference accounts for the two D-lines of sodium. Find the energy difference for D_1 and D_2 lines in electron volts. (Wavelength separation = 6\text{\AA}, Mean wavelength = 5893\text{\AA})

How do characteristic X-ray lines originate? Using Bohr's atomic model deduces a relation between the frequencies of the K series X-ray lines and atomic numbers of the emitting elements. Do you expect this relation to be exact?

Discuss how stars are classified on the basis of their spectra. Briefly mention what different informations about stars can be obtained from the study of their spectra.

What are anti-Stokes lines? Do they occur in both Raman and Compton scatterings? Explain how they arise and how temperature affects their intensities.

What are the transitions leading to the emission of the D lines of Sodium? Deduce the expression for the Lande splitting factor. g and calculate its values for the states involved in the emission of D lines. Hence find the change of energies of these levels when a sodium source is placed in a magnetic field which is not too high.

Write an explanatory outline of thermal ionization of atoms and the spectra of stars, specifying what information we get from the latter.

What is meant by L-S coupling? Deduce the spectral terms which can arise from 3p4p electron configuration. Would all these terms exist in 3\mathrm{p}^2 configuration? Write expressions for the square of angular momentum for L=2 and also for the component of angular momentum for \mathrm{m}_j=2 as given by quantum mechanics.