Waves Sound and Light
Every wave question you'll get on this topic reduces to one idea: energy travels, matter doesn't. Once that's locked in, the rest is bookkeeping — matching frequency to energy, matching medium to wave type, matching angle to the normal. The exam bank for this unit leans hard on data tables (EM spectrum values), applied scenarios (hospitals, tunnels, sonar) and 'explain using wave properties' questions — so these notes are built around calculation plus reasoning, not just definitions.
Overview — How This Topic Fits Together
A wave transfers energy from one place to another without transferring matter. Sound and light are the two waves you'll be tested on most, and they sit at opposite ends of a key divide: sound is a mechanical wave (needs a medium — solid, liquid or gas), light is an electromagnetic wave (travels through vacuum at ). Almost every question in this unit is really asking you to apply correctly, identify a wave's position in the EM spectrum, or track a ray of light across a boundary.
- The EM spectrum questions in the exam bank are data-heavy — you'll be given frequency/energy/wavelength tables and asked to spot the pattern, not just recall the order.
- Communication and technology questions test why a property (penetration, diffraction, straight-line travel) makes a wave suitable — or unsuitable — for a real application.
- Sound questions almost always hinge on echo timing or medium-dependence of speed.
- Reflection/refraction questions are ray-diagram plus Snell's law — examiners penalise angles measured from the surface instead of the normal every single time.
The shape of the chapter
Command terms this topic tests hardest
| Command term | What it demands | AO | Mark-earning move |
|---|---|---|---|
| State | Give a short factual answer with no supporting argument. | AO1 | One correct fact = full marks; extra unrequested explanation earns nothing. |
| Identify | Name or select the correct item from given information. | AO1 | Must use the exact term (e.g. 'gamma rays', not 'high energy rays'). |
| Explain | Give a reasoned account linking cause to effect. | AO2 | Needs a 'because...' chain — a bare fact with no linking word drops a mark. |
| Deduce | Reach a conclusion from data given in the question, showing the reasoning. | AO2/AO3 | Marks are for the working/logic, not just the final number. |
| Calculate | Obtain a numerical answer showing all working. | AO2 | Correct substitution earns a mark even if the final arithmetic slips — but no working shown caps you at the answer mark only. |
| Justify | Support a conclusion with a specific reason drawn from evidence. | AO3 | A conclusion with no evidence link scores zero, even if the conclusion is correct. |
| Discuss / Evaluate | Present more than one viewpoint and weigh them. | AO3 | One-sided answers cap at half marks — you must acknowledge a counterpoint. |
Key point
Overview