Wavelength and frequency
3 marks · NormalA ripple tank is set up to demonstrate that increasing the frequency of waves changes the observed pattern.
Describe what happens to the wavelength of the water waves when the frequency is increased, and explain your answer using the wave equation.
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Wavelength decreases when frequency increases (if speed constant). Using v = f × λ, for constant speed v, increasing f means λ must decrease.
Also accept: Wavelength becomes shorter; As frequency increases, and if speed is constant, wavelength is less
Common mistakes: Thinking wavelength increases
Show mark scheme and worked solution
Marking points
B1 · 1 mark · Describes that wavelength decreases when frequency increases (for constant v).
M1 · 1 mark · Refers correctly to the wave equation (v = f × λ).
M1 · 1 mark · Explains for constant v, λ must decrease if f increases.
Worked solution
If the wave speed stays constant, increasing frequency (f) in the equation v = f × λ means the wavelength (λ) must become smaller so the product stays the same. So wavelength decreases.