The half-unit in one line
How a disturbance travels through a medium, what happens when it is trapped between two ends, and how we hear the result. Waves and optics is worth 8 of Physics's 50 questions over six chapters; this map covers the three wave-and-sound ones, and the optical three have their own map at Optics.
Electrostatics used to sit in this note. The 2026 revision moved sound into Waves and optics and left Electrostatics and capacitors as a unit of its own, so that ground now belongs to Electrostatics and capacitors — go there for Coulomb's law, field, potential and capacitors.
The chapters
| Chapter | What it covers | Read |
|---|---|---|
| Wave motion | Progressive waves and the wave equation, and the speed of sound in solids, liquids and gases with the factors that change it | 12 min |
| Stationary waves | How a standing wave forms, and the harmonics and overtones a string, a closed pipe and an open pipe each allow | 12 min |
| Acoustic phenomena | Pressure amplitude, intensity, loudness, pitch and quality, beats, and the Doppler effect with its medical uses | 15 min |
About forty minutes in all — the shortest reading block in Physics, and a reasonable one to open the subject with if mechanics feels daunting.
Read in this order
Syllabus order is the only sensible order here, because each chapter is built from the one before it.
Wave motion comes first: it defines wavelength, frequency, phase and superposition, and it is also the chapter the optics half quietly assumes. Stationary waves is superposition applied to two waves travelling in opposite directions, so it cannot be read first. Acoustic phenomena then measures what the first two describe — intensity and loudness, beats between two close frequencies, and the Doppler shift.
If you are reading the whole unit, take these three before Optics. Interference, diffraction and polarisation are the same wave ideas moved to light, and they read far faster once sound has taught them.
How it is asked
MEC sets the paper roughly half recall, a third understanding and a fifth application. Recall here is the audible range, a unit, or which harmonics a closed pipe allows. Understanding is why sound travels fastest in solids, why an open pipe sounds an octave above a closed pipe of the same length, or why loudness and intensity are not the same thing. Application is a frequency from a pipe length, a beat frequency, or a Doppler shift — and in Nepal's medical paper, the Doppler question is as likely to be about blood flow as about a passing train.
Sound is also the half of the unit where a stale figure costs a mark: speeds, audible limits and intensity references are all quoted values, and each chapter note gives them with the condition they were measured under.
Then practise
Each chapter has a fixed-length chapter test under Practice › Topics, drawn from questions written to that chapter's scope.