Use sound as a mechanical wave
Sound is longitudinal and needs particles to transfer vibrations. Ultrasound has a frequency above the human hearing range and can be used for imaging and cleaning because it reflects at boundaries or transfers energy.
GCSE Physics resources
AQA GCSE Waves
Sound, Ultrasound and the Ear
Sound is longitudinal and needs particles to transfer vibrations. Ultrasound has a frequency above the human hearing range and can be used for imaging and cleaning because it reflects at boundaries or transfers energy.
Start here
The quick revision snapshot
Sound is longitudinal and needs particles to transfer vibrations. Ultrasound has a frequency above the human hearing range and can be used for imaging and cleaning because it reflects at boundaries or transfers energy.
By the end, you should be able to…
- Explain use sound as a mechanical wave using precise physics language.
- Apply the relevant equations, diagrams or practical method to an exam-style situation.
- Use the mini quizzes and practice answers to identify and correct a misconception.
Core learning content
Learn the idea before you practise it
Start with this short teaching sequence for Sound, Ultrasound and the Ear. Read the model, use the visual, then test your recall before moving into examples and exam practice.
Build the picture
Sound is a longitudinal mechanical wave, so it needs particles and cannot travel through a vacuum. Ultrasound has a frequency above human hearing. Reflections from boundaries between materials can be timed to locate an object or build an image.
Use the right relationship
Choose a relationship because of the physical change in the question, not because it is familiar. Wave speed: v = fλ (m/s, Hz, m). Period: T = 1 ÷ f (s, Hz). Magnification: magnification = image height ÷ object height (no unit). Keep the unit next to each value while you substitute.
What a strong answer does
Use compression/rarefaction language, state the frequency condition and link the application to reflection or energy transfer. Before writing, underline the command word and identify the information that matters. Keep a calculation as equation, substitution and answer with unit; keep an explanation as a linked chain using because, so or therefore. Finish by checking that the final sentence answers the exact context in the question and that the number, direction or conclusion agrees with the evidence given.
Retrieval practice
Quick checks
Answer without looking back first. The feedback explains the model, so a wrong answer still helps you learn.
Mini quiz 1
Check the core idea
Mini quiz 2
Apply the model
Mini quiz 3
Use exam precision
Try it
Sound and ultrasound model
Why can ultrasound be used for imaging even though humans cannot hear it?
What to notice: the readout and written explanation remain available if you do not use the controls.
Worked examples
See the method being built
Cover the answer, attempt the method and then compare your physics language as well as the number.
Example 1 · No sound in space
Explain why astronauts need radios in space.
- Sound needs particles.
- Space is near vacuum.
- Radio waves are electromagnetic.
Show the answer
Sound cannot travel through a vacuum because there are no particles to vibrate; radios use electromagnetic waves.
Example 2 · Ultrasound distance
An ultrasound pulse returns after 0.020 s; speed in tissue 1500 m/s. Find boundary distance.
- Total path = vt.
- 1500 × 0.020 = 30 m round trip.
- Divide by 2.
Show the answer
Distance = 15 m.
Example 3 · Ear response
Explain why very loud sound can damage hearing.
- Larger amplitude means stronger vibrations.
- Link to eardrum/hair cells.
- State potential damage.
Show the answer
Large-amplitude vibrations can damage sensitive structures in the ear.
Misconception clinic
Common wrong turns
Each of these is tempting because it sounds almost right. Replace it with the precise physics before you meet it in a question.
- Calling sound an electromagnetic wave.
- Using total echo distance as depth.
- Mixing pitch (frequency) with loudness (amplitude).
Independent practice
Exam-style questions
Use the working space first. Reveal the guidance only after you have committed to an answer, then improve the exact part that would gain the next mark.
1. State whether sound is transverse or longitudinal.
[1 mark]Show answer and marking guidance
Longitudinal.
2. State why sound cannot travel in a vacuum.
[1 mark]Show answer and marking guidance
It needs particles to transfer vibrations.
3. Define ultrasound.
[2 marks]Show answer and marking guidance
Sound with frequency above the upper limit of human hearing.
4. State one use of ultrasound.
[1 mark]Show answer and marking guidance
Imaging, cleaning or detecting flaws.
5. Explain how ultrasound imaging works.
[3 marks]Show answer and marking guidance
Pulses reflect at boundaries; echo times are used to locate structures.
6. State what amplitude of a sound wave relates to.
[1 mark]Show answer and marking guidance
Loudness/energy transfer, not pitch.
Questions pupils ask
GCSE Physics FAQs
What is the key idea in Sound, Ultrasound and the Ear?
A wave transfers energy without transferring matter overall. Use diagrams to keep amplitude, wavelength, frequency, speed and direction distinct.
How should I practise Sound, Ultrasound and the Ear?
Read the snapshot, attempt the worked examples without looking, complete the mini quizzes and then use the practice questions to check your wording and method.
Next step
Keep your revision moving
Physics sticks when you move between explanation, retrieval and application.