The wave equation
3 marks · NormalDescribe what happens to the wavelength of water waves in a ripple tank if the frequency of the waves is increased while the wave speed remains the same.
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The wavelength decreases when frequency increases, if wave speed stays the same.
Also accept: As frequency increases, wavelength decreases because wave speed is constant.
Common mistakes: Saying amplitude changes instead of wavelength.
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Marking points
B1 · 1 mark · States wavelength decreases as frequency increases.
B2 · 1 mark · States wave speed is constant.
B3 · 1 mark · Gives correct reasoning using the wave equation: .
Worked solution
If wave speed is constant and frequency is increased, the wavelength must decrease according to the equation .