Introduction to Waves (Edexcel GCSE Physics)
Revision Note
Waves & Energy
Waves transfer energy and information
Waves are described as oscillations or vibrations about a fixed point
For example, ripples cause particles of water to oscillate up and down
Sound waves cause particles of air to vibrate back and forth
In all cases, waves transfer energy without transferring matter
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Examples of Waves
Objects floating on water provide evidence that waves only transfer energy and not matter
Worked Example
The diagram below shows a toy duck bobbing up and down on top of the surface of some water, as waves pass it underneath.
Explain how the toy duck demonstrates that waves do not transfer matter.
Answer:
Step 1: Identify the type of wave
The type of wave on the surface of a body of water is a transverse wave
This is because the duck is moving perpendicular to the direction of the wave
Step 2: Describe the motion of the toy duck
The plastic duck moves up and down but does not travel with the wave
Step 3: Explain how this motion demonstrates that waves do not transfer matter
Both transverse and longitudinal waves transfer energy, but not the particles of the medium
This means when a wave travels between two points, no matter actually travels with it, the points on the wave just vibrate back and forth about fixed positions
Objects floating on the water simply bob up and down when waves pass under them, demonstrating that there is no movement of matter in the direction of the wave, only energy
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