Physics Optional

Physics Optional




(a) Mechanics of Particles : Laws of motion; conservation of energy and momentum, applications to rotating frames, centripetal and Coriolis accelerations; Motion under a central force; Conservation of angular momentum, Kepler’s laws; Fields and potentials; Gravitational field and potential due to spherical bodies, Gauss and Poisson equations, gravitational self-energy; Two-body problem; Reduced mass; Rutherford scattering; Centre of mass and laboratory reference frames.

(b) Mechanics of Rigid Bodies : System of particles; Centre of mass, angular momentum, equations of motion; Conservation theorems for energy, momentum and angular momentum; Elastic and inelastic collisions; Rigid Body; Degrees of freedom, Euler’s theorem, angular velocity, angular momentum, moments of inertia, theorems of parallel and perpendicular axes, equation of motion for rotation; Molecular rotations (as rigid bodies); Di and tri-atomic molecules; Precessional motion; top, gyroscope.

(c) Mechanics of Continuous Media : Elasticity, Hooke’s law and elastic constants of isotropic solids and their inter-relation; Streamline (Laminar) flow, viscosity, Poiseuille’s equation, Bernoulli’s equation, Stokes’ law and applications.

(d) Special Relativity : Michelson-Morely experiment and its implications; Lorentz transformations length contraction, time dilation, addition of relativistic velocities, aberration and Doppler effect, mass-energy relation, simple applications to a decay process. Four dimensional momentum vector; Covariance of equations of physics.

2. Waves and Optics :

(a) Waves : Simple harmonic motion, damped oscillation, forced oscillation and resonance; Beats; Stationary waves in a string; Pulses and wave packets; Phase and group velocities; Reflection and refraction from Huygens’ principle.

(b) Geometrial Optics : Laws of reflection and refraction from Fermat’s principle; Matrix method in paraxial optic-thin lens formula, nodal planes, system of two thin lenses, chromatic and spherical aberrations.

(c) Interference : Interference of light -Young’s experiment, Newton’s rings, interference by thin films, Michelson interferometer; Multiple beam interference and Fabry Perot interferometer.

(d) Diffraction : Fraunhofer diffraction - single slit, double slit, diffraction grating, resolving power; Diffraction by a circular aperture and the Airy pattern; Fresnel diffraction: half-period zones and zone plates, circular aperture.

(e) Polarisation and Modern Optics : Production and detection of linearly and circularly polarized light; Double refraction, quarter wave plate; Optical activity; Principles of fibre optics, attenuation; Pulse dispersion in step index and parabolic index fibres; Material dispersion, single mode fibers; Lasers-Einstein A and B coefficients. Ruby and He-Ne lasers. Characteristics of laser light-spatial and temporal coherence; Focusing of laser beams. Three-level scheme for laser operation; Holography and simple applications.

3. Electricity and Magnetism :

(a) Electrostatics and Magnetostatics : Laplace and Poisson equations in electrostatics and their applications; Energy of a system of charges, multipole expansion of scalar potential; Method of images and its applications. Potential and field due to a dipole, force and torque on a dipole in an external field; Dielectrics, polarisation. Solutions to boundary-value problems-conducting and dielectric spheres in a uniform electric field; Magnetic shell, uniformly magnetised sphere; Ferromagnetic materials, hysteresis, energy loss.

(b) Current Electricity : Kirchhoff's laws and their applications. Biot-Savart law, Ampere’s law, Faraday’s law, Lenz’ law. Self-and mutual-inductances; Mean and rms values in AC circuits; DC and AC circuits with R, L and C components; Series and parallel resonance; Quality factor; Principle of transformer.

4. Electromagnetic Waves and Blackbody Radiation : Displacement current and Maxwell’s equations; Wave equations in vacuum, Poynting theorem; Vector and scalar potentials; Electromagnetic field tensor, covariance of Maxwell’s equations; Wave equations in isotropic dielectrics, reflection and refraction at the boundary of two dielectrics; Fresnel’s relations; Total internal reflection; Normal and anomalous dispersion; Rayleigh scattering; Blackbody radiation and Planck ’s radiation law- Stefan-Boltzmann law, Wien’s displacement law and Rayleigh-Jeans law.

5. Thermal and Statistical Physics :

(a) Thermodynamics : Laws of thermodynamics, reversible and irreversible processes, entropy; Isothermal, adiabatic, isobaric, isochoric processes and entropy changes; Otto and Diesel engines, Gibbs’ phase rule and chemical potential; Van der Waals equation of state of a real gas, critical constants; Maxwell- Boltzmann distribution of molecular velocities, transport phenomena, equipartition and virial theorems; Dulong-Petit, Einstein, and Debye’s theories of specific heat of solids; Maxwell relations and application; Clausius-Clapeyron equation. Adiabatic demagnetisation, Joule-Kelvin effect and liquefaction of gases.

(b) Statistical Physics : Macro and micro states, statistical distributions, Maxwell-Boltzmann, Bose-Einstein and Fermi-Dirac Distributions, applications to specific heat of gases and blackbody radiation; Concept of negative temperatures.


1. Quantum Mechanics : Wave-particle duality; Schroedinger equation and expectation values; Uncertainty principle; Solutions of the one-dimensional Schroedinger equation for free particle (Gaussian wave-packet), particle in a box, particle in a finite well, linear harmonic oscillator; Reflection and transmission by a step potential and by a rectangular barrier; Particle in a three dimensional box, density of states, free electron theory of metals; Angular momentum; Hydrogen atom; Spin half particles, properties of Pauli spin matrices.

2. Atomic and Molecular Physics : Stern-Gerlach experiment, electron spin, fine structure of hydrozen atom; L-S coupling, J-J coupling; Spectroscopic notation of atomic states; Zeeman effect; Franck-Condon principle and applications; Elementary theory of rotational, vibrational and electronic spectra of diatomic molecules; Raman effect and molecular structure; Laser Raman spectroscopy; Importance of neutral hydrogen atom, molecular hydrogen and molecular hydrogen ion in astronomy. Fluorescence and Phosphorescence; Elementary theory and applications of NMR and EPR; Elementary ideas about Lamb shift and its significance.

3. Nuclear and Particle Physics : Basic nuclear properties-size, binding energy, angular momentum, parity, magnetic moment; Semi-empirical mass formula and applications. Mass parabolas; Ground state of a deuteron, magnetic moment and non-central forces; Meson theory of nuclear forces; Salient features of nuclear forces; Shell model of the nucleus - success and limitations; Violation of parity in beta decay; Gamma decay and internal conversion; Elementary ideas about Mossbauer spectroscopy; Q-value of nuclear reactions; Nuclear fission and fusion, energy production in stars. Nuclear reactors. Classification of elementary particles and their interactions; Conservation laws; Quark structure of hadrons : Field quanta of electroweak and strong interactions; Elementary ideas about unification of forces; Physics of neutrinos.

4. Solid State Physics, Devices and Electronics : Crystalline and amorphous structure of matter; Different crystal systems, space groups; Methods of determination of crystal structure; X-ray diffraction, scanning and transmission electron microscopies; Band theory of solids—conductors, insulators and semi-conductors; Thermal properties of solids, specific heat, Debye theory; Magnetism: dia, para and ferromagnetism; Elements of super-conductivity, Meissner effect, Josephson junctions and applications; Elementary ideas about high temperature super-conductivity. Intrinsic and extrinsic semi-conductors- p-n-p and n-p-n transistors; Amplifiers and oscillators. Op-amps; FET, JFET and MOSFET; Digital electronics-Boolean identities, De Morgan’s laws, Logic gates and truth tables. Simple logic circuits; Thermistors, solar cells; Fundamentals of microprocessors and digital computers.

How to prepare for physics optional for IAS?

One of the science optional subjects offered by UPSC is physics. It is not a very popular subject like public administration or geography or any other mostly preferred optional subject. Physics optional subject can be taken only by few because it requires prior conceptual clarity. Thus candidates with a science or engineering background can opt for it.

Also, it is one of the best optional subjects for engineering students because they have studied it during the time of their graduation. In addition to this, it is an objective subject so you don’t need any subjective interpretations. Given below are a few things that can be kept in mind while doing the preparation.

1. The syllabus of physics optional is well defined. So be precise while you are studying and confine yourself to the syllabus. There are topics that are not the part of syllabus still a candidate studies it. This leads to sheer wastage of time. So make sure while you are preparing you to stick to the boundaries of the syllabus. Don’t waste your energy on topics that are not the part of syllabus. Thus put in all efforts to prepare what has been asked by syllabus and not other irrelevant topics. Systematically cover every topic of the syllabus in a smooth manner.

2. Start doing answer writing practice. Devote some time to write an answer to the questions. This practice will help you to perform well in the final exam. Since a candidate knows how to write properly in a given time period. This will help you to save time as well in the final exam. This saved time can be utilized while answering other lengthy questions of the paper. In this way, you will be able to solve the paper within the given time period. Also writing answers will enhance the skills of writing well which can be used in other subjects as well.

3. While answering the questions use diagrams to explain the concepts. This makes it easier for the examiner to check your answer. Since the diagram itself will give the gist of the answer. Thus there are high chances of getting good marks for the answers. Also, make neat diagrams. They should be self-explanatory in such a way that examiner gives you full mark just by looking at the diagrams and don’t need to read the content.  Also, try to write important answers in the form of points instead of making long paragraphs for answers. Paragraphs make the answer look jumbled. While on the other hand, points give a clear picture of answers.

4. Another important aspect is to solve previous year question papers. It is a must thing to do. Before appearing for the final exam, a candidate should be well versed with the questions asked in the last few years. This helps to differentiate as to what are the topics that are frequently asked in the exam. Also, it helps in bifurcation the syllabus into strength and weakness. It is also important for the candidates in order to know what the topics which require more focus are. Also, it helps to know other areas of the syllabus that are not so important and doesn’t require much attention. 

5. In addition to this try to attempt as many mock tests as possible. This will help a candidate to know where candidate stands among other students. Also by solving an ample amount of questions of botany optional, a candidate gets an idea as to what kind of questions can be asked in the final exam. There are several institutes which provide mock test series. A candidate can enroll in these tests and can appear for them on a weekly or monthly basis. This will boost your preparation and helps to gain confidence. A candidate gets familiar with how to attempt the question paper in a limited time frame. This also develops the time management skills in the candidate.

6. A candidate can refer to various reference books and study material provided by various coaching institutes. These books help to clear the concepts of the syllabus by giving a detailed explanation. Also, a variety of books gives multiple choices to the candidate to study from. Try to keep your basics strong and develop a proper understanding of the topic. Most of the questions are practical and application-based. So if your basics are not clear then you will not be able to attempt such kind of questions. Thus these reference books are a tool to clear the basic concepts.

7. These varieties of books indeed are helpful but at the same time, it is important to make notes. Notes making helps you in the long run and develops a proper understanding. Reading books of thousands of pages before the exam is not possible. To tackle this last moment confusion and chaos, notes play a significant role. The fat books can be reduced to a thin notebook. These last-minute revision notes help a lot to revise concepts before the exam. Since revision is most important, therefore proper notes making is also necessary for fruitful results and score well in the final exam.

8. While doing preparation it is always better to figure out the most important topics by solving previous year question papers. After identifying the most important topics start focusing on them. It is because most of the questions are asked from that particular topic. It is the right strategy in order to score well. After preparing these topics, prepare for those which are not so important so as to be on a safer side. In this way, you can cover the whole syllabus in a more systematic manner and chances of scoring well will be more. Also don’t skip any topic you never know questions might come from the topics which you didn’t cover. So don’t leave any single topic. You can divide the topics as important but this doesn’t mean you will end up leaving topics that are not so important.