AQA GCSE Evidence for waves(Physics)
Evidence for Waves
You need to be able to describe evidence that in the following situations it is the wave and not the water or air which moves:
1.Ripples on water
2.Sound waves
So, lets look at these
Ripples on water
When a pebble is dropped into a pond, ripples spread outward, but the water itself does not move away from the source.
Floating objects (e.g., a cork or a small leaf) bob up and down rather than moving away with the wave. This shows that the water oscillates in place while the wave energy moves outward.
Sound waves in air
When a speaker emits a sound, sound waves travel through the air to the listener, but the air itself does not move from the speaker to the listener.
If air moved with the wave, wind would be created every time a sound is produced.
A vibrating tuning fork demonstrates this: it produces compressions and rarefactions in the air, but the air molecules only oscillate back and forth—they do not travel with the sound.
Conclusion for Both.
In both cases, the particles of the medium (water or air) oscillate around a fixed position, but the energy of the wave moves forward.
This is characteristic of mechanical waves, where the medium allows the wave to pass through but does not move with it.
Practice Question
1.Describe evidence that shows it is the wave which moves when ripples are seen on the surface of water.
2.Describe evidence that shows it is the wave which moves when ripples are seen on the surface of water.
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Niels Bohr changing the Nuclear Model
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Random nature of radioactive decay
Radioactive contamination or irradiation
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Studies on the effects of radiation on humans
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