Physics · contents

The course

Twenty-five modules, from where a thrown ball lands to how a processor works. Each one is a single standalone page: interactive benches, prediction gates that lock the section until you answer, and a short library of Feynman chapters, Lewin lectures and PhET simulations at the end.

Modules25, all built

LevelClass 10 → class 12 CBSE, taken in depth

Benches90-odd interactive

MathsNothing beyond class 12. Calculus only where it earns its place.

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How the modules connect

The order matters, but not because each module needs the one before it. It matters because a handful of ideas keep coming back in new places, and the course is arranged so that when one returns you have already met it somewhere easier. Pick a strand below and see where it runs.

The mapchoose a strand and watch it run through the course

Every arrow is a place where a later module uses an earlier one directly, not just in spirit.

Mechanics

1 · Two directions, one law

Motion in two dimensions. Horizontal and vertical are independent, and that one sentence is the whole of projectile motion.

01-two-directions-one-law.html

2 · What cannot change

Momentum, and the idea of a conserved quantity: something you can add up before and after and get the same answer, even when you have no idea what happened in between.

02-what-cannot-change.html

3 · Motion, and what causes it

The three equations of motion, and Newton's three laws. The third law gets rebuilt more slowly in Module 6.

03-motion-and-what-causes-it.html

4 · Gas laws, from the inside

Boyle and Charles derived from molecules banging on walls, rather than asserted as laws to memorise.

04-gas-laws-from-the-inside.html

5 · Energy in all its disguises

Work, the energy ledger, conservation. The ledger is opened here and never closes — it is still balancing in Module 24.

05-energy-in-all-its-disguises.html

6 · Going in circles

Circular motion and v²/r derived properly, Newton's third law re-explained from the ground up, banked bends, gravitation, orbits and weightlessness.

06-going-in-circles.html

Waves, heat, light and matter

7 · Wobbles and waves

Simple harmonic motion, resonance, travelling waves, sound, superposition, beats, standing waves and Doppler. The standing-wave section is the doorway to Module 22.

07-wobbles-and-waves.html

8 · Heat and the arrow of time

Temperature against heat against internal energy, specific and latent heat, entropy by counting, Carnot engines and fridges. The Boltzmann factor from here runs the Sun and the transistor.

08-heat-and-the-arrow-of-time.html

9 · Light, as rays

Reflection and the half-height mirror, Snell from Fermat, total internal reflection, lenses and the eye, dispersion, rainbows and the blue sky.

09-light-rays.html

10 · Spin

Torque, moment of inertia, the rolling race, angular momentum, the spinning chair, and why bicycles really stay up.

10-spin.html

11 · Squeeze and flow

Pressure and the hydrostatic paradox, Archimedes, Bernoulli and the venturi, viscosity, surface tension, and an honest account of how a wing lifts.

11-squeeze-and-flow.html

12 · Light, as waves

Two-source interference, Young's fringes and their λD/d spacing (λ is the wavelength), single-slit diffraction and the Rayleigh limit, thin films, polarisation and the three-filter puzzle. Module 21 comes back and breaks it; Module 25 uses the resolution limit to make chips.

12-light-waves.html

Electromagnetism

13 · Charge at rest

Coulomb, electricity against gravity, the field idea, field lines, conductors and the Faraday cage, potential, capacitors, and energy stored in the field.

13-charge-at-rest.html

14 · Charge on the move

Drift velocity against signal speed, resistance and resistivity, series and parallel, Kirchhoff, EMF and internal resistance, I²R and transmission, the RC curve, and electrical safety.

14-charge-on-the-move.html

15 · Magnetism

F = qvB and circular paths, mass spectrometers, F = BIL, the motor and its commutator, fields from currents, domains — and the first hint that magnetism is relativity.

15-magnetism.html

16 · Induction — the law

Flux, Faraday's law, Lenz's law argued from energy conservation, and the magnet that falls slowly down a copper pipe, with motional EMF told twice.

16-induction-the-law.html

17 · Induction — the machines

The law turned into machinery: the rod on rails, the generator and RMS, transformers, and the grid that carries the result to your house.

17-induction-the-machines.html

18 · Maxwell's children

The four equations, the capacitor puzzle that forces the displacement current, the bootstrap, the speed of light falling out of two bench constants, the spectrum, and how an aerial actually radiates.

18-maxwells-children.html

19 · Relativity — what has to give

The two postulates, the light clock, simultaneity, length contraction and the muons that reach sea level — kept, at the cost of absolute time.

19-relativity-what-has-to-give.html

20 · Relativity — fields and forces

E = mc², GPS, and the promise kept: the calculation showing that magnetism is electricity seen from a moving frame.

20-relativity-fields-and-forces.html

The modern half

21 · The quantum, part I

The photoelectric effect, photons and E = hf, Planck's constant measured from a Millikan plot, de Broglie, and electrons sent through two slits one at a time — with the which-path detector switched on and off.

21-quantum-one.html

22 · The quantum II — the atom

Confinement makes integers: the particle in a box from Module 7's string, the hydrogen atom and its spectrum, and orbitals sampled from |ψ|², where ψ is the electron's wave.

22-quantum-two-the-atom.html

23 · The quantum II — uncertainty and tunnelling

The same wave picture turned on the electron's position: uncertainty derived from Module 12's slit, why matter takes up space, tunnelling, and the laser.

23-quantum-two-uncertainty-and-tunnelling.html

24 · The nucleus

Rutherford's back-scattered alphas, the strong force, binding energy and the curve that peaks at iron, radioactivity and half-life, fission and the chain, and why the Sun burns at all when it is far too cold to.

24-nucleus.html

25 · Silicon

Where every strand collides: bands from standing waves, the Boltzmann factor setting the carrier count, doping, the Hall effect proving holes are real, the junction, the transistor, and a NAND gate solved from the transistor equations.

25-silicon.html

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How to use one of these

Each module is a single HTML file with everything inside it. No internet connection is needed to read one, and nothing is installed. Open it in any browser, on a laptop or a phone.

The benches are the point. Every one of them computes its numbers from the simulation actually running, not from a formula printed on the page. When a bench says a ratio comes out at 1.414 or that 2 478 muons survived, that is what the code counted. Push the sliders to their ends; break things deliberately.
The gates lock the page. A section stays hidden until you commit to an answer. Guessing is allowed — the point is to have a prediction on record before you see the result, because that is the only way to find out what you actually believed.
The boxes. In the wild is where the idea shows up in something you own. Deeper is an aside for when you want more. Try it tonight is something to do with your hands, usually with things already in the house.
At source. Every module ends with a short list of the real thing — Feynman's own chapters, Walter Lewin's lectures, PhET's simulations. Nothing on those lists is a summary of a summary, and everything on them is free.

They are meant to be read slowly, and out of order once you have the first few.