UPSC Physics Optional PYQs (CSE & IFoS)PYQs

Describe briefly how parity violation in \beta-decay was experimentally observed? What do you understand by the statement, 'neutrinos are left-handed'?

Write the quark contents and the quantum numbers (B, J, s, I_3) of the following hadrons : \bar{\Sigma}^-, \Xi^\circ, \Pi^+, \bar{K}^\circ

What is meant by quark confinement ? Why are the masses of hadrons larger than the sum of the masses of their constituent quarks ?

Explain briefly SU(3) flavor symmetry and SU(2) isospin symmetry in particle physics.

Given that the deuteron magnetic moment operator (in units of nuclear magneton) can be expressed as \vec{\mu}_d = \mu_n\vec{\sigma}_n + \mu_p\vec{\sigma}_p + \frac{1}{2}\vec{l} where \vec{l} is the relative angular momentum between neutron and proton, \vec{\sigma}_n and \vec{\sigma}_p are the Pauli spin operators and \mu_n and \mu_p are the respective magnetic moments. Find out the D-state probability of deuteron wave function. [Given: \mu_d = 0.857\mu_N, \mu_n = -1.913\mu_N and \mu_p = 2.793\mu_N; \mu_N (nuclear magneton)]

Write the semi-empirical mass formula pointing out the role of volume term, surface energy term, coulomb and symmetry energy correction terms.

Estimate the order of nuclear radius of lead (Z = 82) using the large angle (back) scattering of alpha particles of energy 10\,\mathrm{MeV} incident on a target (lead). [Given: (4\pi\epsilon_0)^{-1} = 9 \times 10^{9}\,\mathrm{N\,m^2\,C^{-2}}]

Distinguish between charge independence and charge symmetry of nuclear force. Give one example of each of these.

What are the quantum numbers of u, d and s quarks and of the corresponding antiquarks (\bar{u}, \bar{d}, \bar{s})? Obtain the quark contents of proton (p), neutron (n), positively charged pion (\pi^+) and negatively charged omega minus (\Omega^-) particle.

What are leptons? How are they different from other baryons? Define their quantum numbers and identify the forbidden ones in the following scattering or decay processes, justifying your conclusions :

(i) \pi^0 \rightarrow \gamma + \gamma

(ii) \pi^0 \rightarrow \gamma + \gamma \rightarrow (e^+ + e^-) + (\mu^- + \mu^+)

(iii) n \rightarrow p + e^- + \bar{\nu}_\mu

(iv) \pi^+ + p \rightarrow p + p + u_\tau + \bar{\nu}_e

(v) u_e + p \rightarrow u_\mu + p + \pi^0

Obtain the Q-values for the following four nuclear reactions :

(i) {}^{14}_{7}\text{N} + ^{4}_{2}\text{He} \rightarrow ^{17}_{8}\text{O} + ^{1}_{1}\text{H}

(ii) {}^{7}_{3}\text{Li} + ^{4}_{2}\text{He} \rightarrow ^{10}_{5}\text{B} + ^{1}_{0}\text{n}

(iii) {}^{6}_{3}\text{Li} + ^{1}_{1}\text{H} \rightarrow ^{3}_{2}\text{He} + ^{4}_{2}\text{He}

(iv) {}^{23}_{11}\text{Na} + ^{1}_{1}\text{H} \rightarrow ^{20}_{10}\text{Ne} + ^{4}_{2}\text{He}

Describe the properties of field quanta of electro-weak and strong interactions of particles.

In a nuclear fusion process, four hydrogen nuclei combine to form a helium nucleus. Obtain the energy released in such a process. If the same process is responsible for energy of a star of mass 2 \times 10^{30}\text{ kg}, each kilogram having 6 \times 10^{26} protons, what could be the magnitude of energy released in it?

Explain why the deuteron has no excited state.

What is parity transformation? Discuss the experiment that confirms the violation of parity in beta decay.

Write down the quark structure of the following hadrons: \Delta^{++}, \Omega^-, \Sigma^- and \Lambda^0 Write down the following decays in terms of quarks:

(i) n \to p + e^- \bar{\nu}_e

(ii) \Delta^+ \to \pi^+ + n

(iii) \Sigma^+ \to p + \pi^0

Give an outline of meson theory of nuclear forces. Describe the physical basis of short-range nuclear repulsion between like nucleons : proton-proton (p\text{-}p) or neutron-neutron (n\text{-}n). Consider the following two three-nucleon systems : (p\text{-}p\text{-}p) and (n\text{-}n\text{-}n). Which one is more likely to form a bound state?

Explain the various leptonic family members. What is leptonic number conservation? Based on this conservation law, state whether the following reactions are possible or not:

(i) \pi^- \to \mu^- \bar{\nu}_\tau

(ii) n \to p + e^- \bar{\nu}_e

What are elementary particles and how are they classified? Describe in brief the different types of interactions that can occur between the elementary particles.

Predict the spin and parity of ground states of the following nuclei on the basis of shell model:

(i) {}_{8}\mathrm{O}^{15}

(ii) {}_{8}\mathrm{O}^{16}

(iii) {}_{17}\mathrm{Cl}^{38}