UPSC Physics Optional PYQs (CSE & IFoS)PYQs

What is Boolean algebra? State De Morgan's theorems and determine the output expressions for the circuit shown below by using De Morgan's theorems :

What is a microprocessor? Briefly mention the basic units of a microprocessor by drawing descriptive block diagram of 8085 microprocessor.

(i) Give a qualitative description of the BCS theory and explain how it accounts for the superconducting state. (ii) The critical field of niobium is 1 \times 10^5\text{ A/m} at 8\text{ K} and 2 \times 10^5\text{ A/m} at absolute zero. Find the transition temperature of the element.

(i) How will you obtain OR gate from NAND gate? Draw the logic circuit for the following expressions : Y = ABC + \bar{D} Y = (\bar{E}G + B)H (ii) What is a thermistor? Explain the working of thermistor by drawing temperature-resistance curve.

What is Josephson effect? How can Josephson junctions be used to produce macroscopic quantum interference?

(i) Explain the Bravais lattice and non-Bravais lattice with suitable diagram. (ii) Draw the (1\ 0\ 0), (1\ 1\ 0) and (1\ 1\ 1) planes in a cubic unit cell. (iii) Obtain the Miller indices of a plane with intercepts a, b/2, 3c in a simple cubic unit cell.

Describe the bandwidth and slew rate of an Op-Amp. The amplifier shown in the below circuit is used to amplify an input signal to a peak output voltage of 100\text{ mV} and its slew rate is 0\cdot 5\text{ V}/\mu\text{s}. What is the maximum operating frequency of the amplifier?

What is an oscillator? Explain the Barkhausen criterion and working principle of an R-C phase-shift oscillator with suitable circuit diagram.

Consider an energy band which is filled with electrons up to a certain value k_1 \left(k_1 < \frac{\pi}{a}\right). Determine the total effective number of free electrons in the energy band. Comment on the electron distribution in an insulator, intrinsic semiconductor and metals at 0\text{ K}. Symbols have their usual meanings.

What do you understand by \text{SU}(3) symmetry for the quark model? On the basis of it, explain that the baryons can have +2 charge but mesons cannot have the same.

Calculate the minimum energy (E_\gamma) required for a gamma ray photon to disintegrate a deuteron of mass M and binding energy B into a neutron and a proton. (Assume B \ll Mc^2)

Using the semi-empirical binding energy formula, establish the relation between atomic number and mass number for a most stable light nucleus. Also, explain which is the most stable nucleus among {}^{3}_{2}\text{He}, {}^{6}_{4}\text{Be} and {}^{6}_{3}\text{Li}. [Given : a_c = 0\cdot 71\text{ MeV}, a_n = 22\cdot 7\text{ MeV} and assume Z(Z-1) \approx Z^2]

By considering a suitable nuclear potential well for the deuteron ground state, show that it is a loosely bound nucleus.

If plutonium ({}^{239}_{94}\text{Pu}) is used as fuel in a fission reactor and is producing fragments barium ({}^{146}_{56}\text{Ba}) and strontium ({}^{91}_{38}\text{Sr}) by initiating the reaction by one neutron and producing three neutrons in the process, then calculate the number of fissions per second required in a 100\text{ MW} reactor. [Given : BE per nucleon (MeV) : 7\cdot 6 for {}^{239}\text{Pu}, 8\cdot 2 for {}^{146}\text{Ba} and 8\cdot 6 for {}^{91}\text{Sr}]

(i) With suitable diagrams, explain the intensity distribution of spectral lines in vibrational-electronic spectra by using the Franck-Condon principle. (ii) Calculate the positions of the first two rotational Raman lines in the spectrum of \text{H}_2, if its bond length is 0\cdot 074\text{ nm}. [Given : {}^{1}\text{H} = 1\cdot 673 \times 10^{-27}\text{ kg}]

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.

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.

(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.

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

Experimental observation for the line spectrum of an atom shows that the separations between adjacent energy levels of increasing energy in a multiplet are in the ratio 3:5. By using the Landé interval rule, assign the quantum numbers L, S and J to these levels.