UPSC Physics Optional PYQs (CSE & IFoS)PYQs

Explain the reduced zone scheme of plotting the energy bands in solids. On the basis of E vs k curve distinguish between conductors, semiconductors and insulators.

A star converts all its hydrogen into helium, achieving 100\% helium. It then converts the helium into carbon via the reaction {}^4_2\text{He} + ^4_2\text{He} + ^4_2\text{He} \xrightarrow{\quad} ^{12}_6\text{C} + 7.27\text{ MeV} The mass of the star is 5.0 \times 10^{32}\text{ kg} and it generates energy at the rate of 5 \times 10^{30}\text{ W}. How long will it take to convert all helium to carbon at this rate ?

Write the quark composition of the following :

(i) Neutron

(ii) Proton

(iii) \Lambda

(iv) \text{K}^-

(v) \pi^+

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

Calculate the binding energy per nucleus for {}^{87}_{38}\text{Sr}.

What are magic numbers ? Discuss the 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 : {}^7_3\text{Li}, \quad {}^{13}_7\text{N}, \quad {}^{17}_8\text{O}, \quad {}^{27}_{13}\text{Al}

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.

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?

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}.

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.

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.

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

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

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?

What is Raman effect ? Discuss its application to molecular structure.

Describe Stern–Gerlach experiment. In performing this experiment, beams of neutral atoms are used. Why are electrons or ion beams not used ? Explain how it demonstrates the discrete nature of the magnetic moment of an atom.

State and explain the Heisenberg's uncertainty principle. Show that the natural line width of a spectral line follows from this principle. The lifetime of an excited state of an atom is 10^{-8}\text{ s}. Calculate the energy width of such a state.