AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Students should be able to describe evidence that, for both ripples on a…
Full specification wording
Transverse and longitudinal waves: Students should be able to describe evidence that, for both ripples on a water surface and sound waves in air, it is the wave and not the water or air itself that travels.
The evidence is that the medium stays where it is while the wave travels on.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 6 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
The evidence is that the medium stays where it is while the wave travels on. On water, a floating object bobs up and down as ripples pass but stays in the same place, and pond weed rocks without being carried to the bank; if the water moved with the wave, the far end of the pond would fill up. For sound, a vibrating drum skin does not push all the air away in front of it, so no vacuum forms behind the wave, and a loudspeaker playing for an hour does not empty the room of air or create a wind. In both cases the particles oscillate about a fixed position, and only energy moves forward. A second sound example is dust or a candle flame near a loudspeaker: it vibrates back and forth about a fixed point rather than being blown across the room, showing the air oscillates but does not travel.
What earns the marks
- A floating object on ripples bobbing up and down but staying in the same place.
- The drum or loudspeaker evidence, that the vibrating surface does not leave a vacuum behind it.
- Stating that the particles oscillate about a fixed position.
- Concluding that the wave transfers energy and not matter.
Common mistakes and how to put them right
Offering that the wind blows the ripples along as evidence about the water.
Describing a moving boat or a moving object as proof that matter travels with the wave.
Claiming air is pushed all the way from the loudspeaker into the listener's ear.
Giving a definition of a wave instead of a piece of observable evidence.
Exam tips
- Name a specific observation, such as a cork bobbing, rather than a general statement about waves.
- Say what would happen if matter did travel, then note that it is not observed.
- One piece of evidence with an explanation usually scores more than three bare statements.
Try the lesson
The start of the Transverse and longitudinal waves: Students should be able to describe evidence that, for both ripples on a water surface and sound waves in air, 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 leaf floats on the surface of a pond. Ripples spread outwards across the pond past the leaf. What happens to the leaf as the ripples pass?
Listen
The evidence is that the medium stays where it is while the wave travels on. On water, a floating object bobs up and down as ripples pass but stays in the same place, and pond weed rocks without being carried to the bank; if the water moved with the wave, the far end of the pond would fill up. For sound, a vibrating drum skin does not push all the air away in front of it, so no vacuum forms behind the wave, and a loudspeaker playing for an hour does not empty the room of air or create a wind. In both cases the particles oscillate about a fixed position, and only energy moves forward. A second sound example is dust or a candle flame near a loudspeaker: it vibrates back and forth about a fixed point rather than being blown across the room, showing the air oscillates but does not travel. A strong answer earns marks for these points. a floating object on ripples bobbing up and down but staying in the same place. the drum or loudspeaker evidence, that the vibrating surface does not leave a vacuum behind it. stating that the particles oscillate about a fixed position. concluding that the wave transfers energy and not matter. Exam tip: Name a specific observation, such as a cork bobbing, rather than a general statement about waves.
Key words
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evidence
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floating objects
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oscillation about a fixed position
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sound and water waves
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See every definition
- evidence
- A specific observation, such as a cork bobbing, that shows the wave and not the water or air itself travels.
- floating objects
- A floating object bobs up and down as ripples pass but stays in the same place, showing the water does not travel with the wave.
- oscillation about a fixed position
- In both cases the particles oscillate about a fixed position, and only energy moves forward.
- sound and water waves
- For ripples on a water surface and sound waves in air, it is the wave and not the water or air itself that travels.
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Test your understanding of Transverse and longitudinal waves: Students should be able to describe evidence that, for both ripples on a water surface and sound waves in air, it is the wave and not the water or air itself that travels.
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