A detailed scientific study of the matter and energy around us including their properties, nature of existence, etc is termed physics. It is a vast subject that has different branches of study like heat forms, light and radiations, sound forms, electromagnetism, study of atoms etc.

**Physics deals with:**

- Mechanics and theories of objects.
- Quantum physics and associated theories.
- Statistical physics.
- Electronics as a sub-element.
- Understanding classical and modern mechanics.

**Physics as an option in UPSC Mains**

- This is a very rigid subject and there are many aspirants who have not been successful in the paper in the very first attempt. Be patient, the first step is to familiarise yourself well with the syllabus.
- Whatever is the prescribed syllabus for the subject, the first step is to stick to it. Just because the subject is tough, does not mean it needs unnecessary piling up of many books. A smart resource organization will definitely do the trick here.
- Since the subjects have too many topics and sub topics to cover, first make a detailed list of all these things.
- It would be wise to choose this subject if you have a background in the subject or you are from a science stream. If you are an engineer and have an interest in the subject, then this is definitely going to be easy for you.
- Attend coaching if you aren’t familiar with the concepts in depth and do not have a detailed knowledge of it. Take one topic at a time.
- Your answers should present the concept on which it is based, a very detailed explanation, supported with accurate terminologies and word usage.
- You can expect straight forward as well as tricky questions in the paper for this subject.

**Preparation tips**

- When it comes to classical mechanics, treat this subject area as one of the most asked and favorite part of examiners. You will compulsorily find questions from this part of the syllabus. Good study materials will guide you through this part without much difficulty.
- When you are dealing with energy and waves section, do not forget relevant diagrams. They help in visual understanding of your answers and help fetch better marks.
- Remember, there are certain areas in this subject that are commonly asked in papers over the years. Do not sit worrying about such questions, be wise to identify the topics based on which those questions keep coming from time to time.
- When it comes to purely theoretical and explanation oriented concepts, it’s a scoring area for you. You could better your answers by illustrating them with simple examples. Take care that examples should be relevant to the concepts you are dealing with. On a lighter note, write down every such example that you come across during preparation and revise it thoroughly later on.
- Practice derivations, formulae and problems without fail. Solve as many problems as you can. Work on your speed in solving problems.
- Try and solve as many previous year papers and mock papers as possible. You will get a very good idea of the difficulty level of problems presented in these papers.

**Points to remember:**

- This subject is not opinion or comment based; it is a pure science subject and deals with raw concepts. Hence, you should take care to choose standard books to present answers that contain relevant words in them.
- Practice derivations well. Do not skip important steps in derivations. Each step presented will fetch you good marks. Explain derivations with relevant terminology.
- Refer at least two books to write down a complete derivation. Put in efforts to make a note of derivations for quick reference later on.
- Start with the core concepts and basic understanding of the subject. This will act as a backbone for your preparation.
- Physics is a problem-oriented subject. Practice problem solving. Try to solve different kinds of questions. Identify the underlying concept to arrive at the relevant formula.
- Do not let yourself into every small space to try out formulae and derivation. Keep your paper clean and tidy.

**Books for reference:**

- Modern physics by A Beiser.
- A textbook of sound by Khanna and Bedi.
- Atomic physics by J B Rajan.
- Classical Mechanism by Gupta.
- EM theory by Chopra and Aggarwal.
- Mechanics by D S Mathur.

**UPSC CSE Mains Physics Syllabus – Explain in detail**

**Paper – I: Physics Syllabus**

**1. (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-Morley 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) Geometrical Optics:** Laws of reflection and refraction from Fermat’s principle; Matrix method in paraxial optics-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) Polarization 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 fibres; 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, polarization; Solutions to boundary-value problems-conducting and dielectric spheres in a uniform electric field; Magnetic shell, uniformly magnetized 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 r m s values in AC circuits; DC and AC circuits with R, L and C components; Series and parallel resonances; Quality factor; Principle of transformer.

(c) 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.

**4. 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-Boltzman 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 applications; 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.

**PAPER – II: Physics Syllabus**

**1. Quantum Mechanics:** Wave-particle dualitiy; Schroedinger equation and expectation values; Uncertainty principle; Solutions of the one-dimensional Schroedinger equation for a 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 hydrogen atom; L-S coupling, J-J coupling; Spectroscopic notation of atomic states; Zeeman effect; Frank- Condon principle and applications; Elementary theory of rotational, vibratonal 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 deuteron, magnetic moment and non-central forces; Meson theory of nuclear forces; Salient features of nuclear forces; Shell model of the nucleus – successes 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 semiconductors; Thermal properties of solids, specific heat, Debye theory; Magnetism: dia, para and ferromagnetism; Elements of superconductivity, Meissner effect, Josephson junctions and applications; Elementary ideas about high temperature superconductivity. Intrinsic and extrinsic semiconductors; pn- 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.

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