Properties of waves — AQA GCSE Physics
Test yourself on Properties of waves with AQA GCSE practice questions.
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Properties of waves explained
Four quantities describe any wave. Amplitude is the maximum displacement of a point from its undisturbed position, measured in metres.
Read the full explanation
Wavelength, λ, is the distance from one point on a wave to the equivalent point on the next, also in metres. Frequency, f, is the number of complete waves passing a point each second, measured in hertz. Period, T, is the time for one complete wave to pass, in seconds, and the two are reciprocals: T = 1 ÷ f. The speed at which the wave carries energy through the medium links three of them, wave speed = frequency × wavelength, so a 50 Hz ripple of wavelength 0.02 m travels at 1 m/s. Amplitude and frequency are independent, so turning up the volume on a signal generator changes the amplitude while the frequency and wavelength stay the same.
Your focus
- Label amplitude, wavelength and period on displacement-distance and displacement-time graphs of a wave.
- Calculate the wave speed of a ripple from its measured frequency and wavelength.
- Convert between the frequency and the period of a wave using T = 1 ÷ f.
Properties of waves exam tips
Marking Points
- one mark for amplitude as the maximum displacement from the undisturbed position
- one mark for wavelength as the distance between equivalent points on adjacent waves
- one mark for frequency as the number of waves passing a point each second, in hertz
- one mark for period as the time for one wave, with T = 1 ÷ f
- one mark for using wave speed = frequency × wavelength with consistent units
Examiner Tips
- 💡Check the axis of a wave graph: a displacement-distance graph shows wavelength, a displacement-time graph shows period.
- 💡Convert every length to metres before using wave speed = frequency × wavelength.
- 💡Label amplitude with an arrow that starts on the centre line, not at a trough.
Common Mistakes
- measuring the amplitude from a crest down to a trough instead of from the undisturbed position
- giving frequency the unit s or m rather than Hz
- confusing the period with the wavelength because both are read off a graph
- writing wave speed = frequency ÷ wavelength