AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Students should be able to describe wave motion in terms of their…
Full specification wording
Properties of waves: Students should be able to describe wave motion in terms of their amplitude, wavelength, frequency and period.
Four quantities describe any wave.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 1 of 7
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Four quantities describe any wave. Amplitude is the maximum displacement of a point from its undisturbed position, measured in metres. 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.
What earns the marks
- Amplitude as the maximum displacement from the undisturbed position.
- Wavelength as the distance between equivalent points on adjacent waves.
- Frequency as the number of waves passing a point each second, in hertz.
- Period as the time for one wave, with T = 1 ÷ f.
- Using wave speed = frequency × wavelength with consistent units.
Common mistakes and how to put them right
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.
Exam 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.
Try the lesson
The start of the Properties of waves: Students should be able to describe wave motion in terms of their amplitude, wavelength, frequency and period. lesson, made from checked teaching notes for this specification point.
Have a go first
Which quantity describes the distance between two neighbouring crests of a wave?
Listen
Four quantities describe any wave. Amplitude is the maximum displacement of a point from its undisturbed position, measured in metres. 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. A strong answer earns marks for these points. amplitude as the maximum displacement from the undisturbed position. wavelength as the distance between equivalent points on adjacent waves. frequency as the number of waves passing a point each second, in hertz. period as the time for one wave, with T = 1 ÷ f. Exam tip: Check the axis of a wave graph: a displacement-distance graph shows wavelength, a displacement-time graph shows period.
Key words
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amplitude
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wavelength
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frequency
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period
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See every definition
- amplitude
- The maximum displacement of a point from its undisturbed position, measured in metres.
- wavelength
- The distance from one point on a wave to the equivalent point on the next, also in metres.
- frequency
- The number of complete waves passing a point each second, measured in hertz.
- period
- The time for one complete wave to pass, in seconds, and is the reciprocal of frequency.
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