Waves, Sound, and Light
MYP Year 3 Sciences — Waves, Sound and Light (Physics strand)
Every question your teacher writes on this topic is really testing one thing: can you tell which wave property is changing, and can you say what that change does? Colour is coded by wavelength, pitch by frequency, loudness by amplitude, brightness by amplitude too — mix those up and you lose marks even when your physics instinct was right. These notes are built around the exact command terms (describe, explain, analyse, predict) that examiners actually use, because half the marks lost on this topic are lost to answering the wrong type of question, not to wrong physics.
Overview — How This Topic Fits Together
A wave transfers energy from one place to another without transferring matter — the medium (or the electromagnetic field, for light) just wobbles in place while the disturbance moves through it. This topic has two halves that keep getting confused with each other: light waves (transverse, no medium needed, travel at m/s in a vacuum) and sound waves (longitudinal, need a medium, travel much slower — about 340 m/s in air).
- Colour and pitch both depend on frequency/wavelength — colour for light, pitch for sound.
- Brightness and loudness both depend on amplitude — how big the vibration or oscillation is.
- Reflection and refraction are what happen when a wave meets a boundary — bounce back, or bend and carry on into a new medium.
- The technology section is really just 'which part of the EM spectrum, or which wave property, is being exploited' applied to real devices.
The shape of the chapter
Command terms this topic actually uses
| Command term | What it demands | AO | Mark-earning move |
|---|---|---|---|
| Describe | Give a detailed, accurate account — usually the trend in data or what physically happens | Knowing & understanding | Must state the actual pattern with real values, not just 'there is a difference'. |
| Explain | Give reasons or causes, using correct topic vocabulary | Understanding & applying | Zero credit if you only restate the description — the 'why' is the mark. |
| Identify | Name or pick out the correct variable/feature from a scenario | Knowing & understanding | A short phrase is enough; extra explanation earns nothing extra. |
| State | Give a short, precise answer with no justification required | Knowing & understanding | One fact only — padding costs time, not marks. |
| Analyse | Break down data to find and interpret a relationship | Processing & evaluating | Must go beyond description — needs 'as X increases, Y…' phrasing. |
| Predict | Use an established pattern to state an outcome not directly given | Processing & evaluating | Answer must follow logically from the trend already found, not be a guess. |
Key point
Overview