Physics · KS3 and GCSE · Interactive lesson
Waves: amplitude, wavelength and frequency
Watch a fixed point move as a transverse wave passes. Compare amplitude, wavelength and frequency, then use the wave-speed equation.
Choose your view
Explore an interactive example, then try the questions at your own pace.
KS3 / GCSE · start with the idea
By the end of this lesson: Distinguish wave height from the number of oscillations each second.
The interactive diagram and controls are in Stage 2, “Explore one example”. Read the idea here, then try it next.
- Wavelength is the distance from one crest to the next.
- Amplitude is the height from the middle line to a crest.
- Frequency counts complete waves passing one fixed point each second.
Useful starting points
These lessons open in a new tab so you can return here.
What do the words mean?
- Crest
- A high point on the wave.
- Hz (hertz)
- Waves per second. 3 Hz means three complete waves pass a point each second.
- λ (lambda)
- A letter used for wavelength.
- Amplitude
- Maximum distance from the middle position. It is half the full crest-to-trough height.
Change the example
This is the lesson example. Your practice question uses its own numbers.
Something to try
Keep the amplitude the same. Increase the frequency and play the motion. Does the wave get taller, or oscillate more often?
Notice what changes
How particle motion works +
Starts paused. Press Play, then add energy to see the warmer particles move faster.
Particles keep the same size. Liquid particles move around; solid particles vibrate around fixed positions. This is a simplified model, with the change in motion exaggerated to make it easier to see.
About the playback +
About this model
The orange bracket marks one full wave: one wavelength. The middle line shows where the point would be with no wave. Speed stays fixed at 12 m/s; the height uses a comparison scale, not a measured length. Play in slow motion: the orange point stays at 6 m and moves up and down; it does not travel along with the wave. This shows a transverse wave: the point moves at right angles to the direction the wave travels. Sound particles move back and forth along the direction of travel instead. Playback takes four real seconds for each second shown.
More about this diagram
Still picture. Play particle motion in Stage 2.
3 waves per second · wavelength 4 m
Still picture of the example from Stage 2. Use the back arrow to change it.
Work through it
Starting example: read the steps below
- Frequency 3 Hz means 3 complete waves pass a point each second.
- The orange bracket spans one wavelength: 4 metres.
- Amplitude measures from the middle line to a crest. To change this height, return to the interactive example and change amplitude.
- Wave speed stays fixed here. In the interactive example, changing frequency changes wavelength; changing amplitude changes wave height.
Try on your own
Your turn. No rush.
Question 1
A wave has frequency 3 Hz. How many complete waves pass a fixed point each second?
About these questions
Questions appear in a mixed order. Work at your own pace and stop whenever you like.
These questions use their own numbers, separate from the lesson example. You can stop whenever you like. Answers last for this visit to the page.
A good place to pause
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Can you tell amplitude, wavelength and frequency apart?
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Notes for parents and tutors
These lessons cover selected KS3 and GCSE ideas for England; they are not a complete course. The level notes explain where GCSE methods or optional extensions begin. Maurice can help you choose material for your course and exam board.
The content draws on the DfE Maths curriculum, DfE Science curriculum and AQA GCSE Physics specification. Level labels are guidance, not exam-board endorsements. For AQA Radioactivity, calculating net decline as a ratio is Higher-tier work. Net means the overall change; ask Maurice whether this extension is relevant to your course. Explanations and practice were reviewed during development on 21 October 2026; Maurice should check their fit before assigning work.
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