Pearson Edexcel · GCSE · Physics
Course version: 1PH0 · Version from Sept 2016
Describe evidence that with water and sound waves it is the wave and not…
Full specification wording
Topic 4 – Waves: 4.2 Describe evidence that with water and sound waves it is the wave and not the water or air itself that travels
A wave transfers energy and information through a medium while the medium itself stays in place.
Checked against the Pearson Edexcel 1PH0 specification (opens in a new tab) on .
- Point 2 of 15
Study notes
From the checked teaching notes for this specification point.
The idea
A wave transfers energy and information through a medium while the medium itself stays in place. For water waves, a floating cork or a droplet bobs up and down as a ripple passes but does not travel along with the ripple, so the water oscillates about a fixed position while the wave pattern moves outward. For sound, air particles vibrate back and forth about fixed positions and pass the disturbance to neighbours; the compression travels but the air does not move from source to ear. A smoke or dust trace, or a loudspeaker cone pushing air, shows the same point. The evidence is that the medium oscillates locally while the wave disturbance propagates, so the wave, not the water or air, travels.
What earns the marks
- States that a floating object on water bobs up and down as a wave passes without moving along with the wave.
- Explains that water particles oscillate about fixed positions while the wave pattern travels outward.
- States that air particles vibrate about fixed positions and pass the disturbance to neighbouring particles.
- Identifies that the compression or sound energy travels through the air while the air itself does not move from source to listener.
- Concludes that the wave transfers energy through the medium while the medium stays in place.
Common mistakes and how to put them right
Claims that the water moves along with the wave.
Put it right by noting the cork bobs in place while the wave pattern moves.
Asserts that air travels from the source to the ear.
Put it right by explaining that air particles oscillate locally and pass on the disturbance.
Treats the medium and the wave as the same thing.
Put it right by separating the oscillating particles from the travelling disturbance.
Exam tips
- Name a concrete observation, such as a cork bobbing on water, to support the claim.
- State clearly that the medium oscillates about a fixed position while the wave moves.
- Use the word energy to describe what the wave carries through the medium.
Try the lesson
The start of the Topic 4 – Waves: 4.2 Describe evidence that with water and sound waves it is the wave and not the water or air itself that travels lesson, made from checked teaching notes for this specification point.
Have a go first
A small ball floats on water in a ripple tank. A water wave passes beneath it. What does the ball do?
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