UPSC Physics Optional PYQs (CSE & IFoS)PYQs

Discuss the four basic types of fundamental interactions in nature and compare them.

Describe the quark model. Obtain the quark composition of baryons and mesons.

Obtain the ground-state wave function, depth of potential and range of nuclear force in deuteron and discuss. Also prove that no bound state exists for l \neq 0.

Compute the density of a typical nucleus and find the resultant mass, if we could manufacture a nucleus with a radius of 1\text{ cm}.

Discuss the shell model of the nucleus. What are its merits ?

What is kinematics of nuclear reaction ? What is the Q-value and its significance ?

Use Hund's rules to find the ground-state quantum numbers, L and S of (i) Carbon and (ii) Oxygen atoms.

Explain Russel Saunders coupling. Discuss the summation rules for orbital angular momentum, spin angular momentum and total angular momentum quantum numbers.

The observed vibrational frequency of CO molecule is 6.42 \times 10^{13}\ \mathrm{Hz}. What is the effective force constant of the molecule?

Hydrogen molecule is diatomic. Obtain the rotational energy levels of this molecule. Write down the selection rules. Obtain the smallest energy required to excite the lowest rotational mode.

If K, L and M energy levels of platinum are approximately 78, 12 and 3\ \mathrm{keV}, respectively, below the vacuum level, calculate the wavelengths of K_\alpha and K_\beta lines.

Find the magnetic moment of an atom in {}^3P_2 state, assuming that LS coupling holds for this case.

Two successive lines in the rotational emission spectrum of HCl molecule appear at wave numbers 83.5\ \mathrm{cm^{-1}} and 104.1\ \mathrm{cm^{-1}}. Calculate the position of the next line appearing at the higher wave number.

The energy levels of a hydrogen atom are given by E_n = \left(\frac{-1}{n^2}\right)R_{\mathrm{yd}} where 1R_{\mathrm{yd}} = hcR. Show that R = 1.097 \times 10^7\ \mathrm{m^{-1}}.

State the postulates of Bohr regarding his atom model. Obtain the expressions for the radius and electron-energy of the n^\text{th} orbit. Explain how Bohr's atom model successfully accounts for the hydrogen spectrum.

What is 'multiplicity' ? Give the term symbol for the following cases :

(i) S = \frac{1}{2} \qquad L = 2

(ii) S = 1 \qquad L = 1

Distinguish between fluorescence and phosphorescence in electronically excited molecules.

Derive the rotational-vibrational energy levels of a diatomic molecule. Give the analysis of spectral lines.

Obtain Zeeman splitting for sodium D-lines.

Give an account of Heisenberg's Uncertainty principle. Outline an idealised experiment to bring out its significance.