AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Properties of waves: wave speed, v, in metres per second, m/s
Wave speed, v, is the distance a wave crest travels each second, measured in metres per second (m/s).
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 13 of 18
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Wave speed, v, is the distance a wave crest travels each second, measured in metres per second (m/s). It links frequency f in hertz (Hz) and wavelength λ in metres (m) through the equation v = f λ. For example, a wave with f = 50 Hz and λ = 2 m has v = 50 × 2 = 100 m/s. You can also measure v directly: time a crest over a known distance, or use a ripple tank and stopwatch. In exams, you may calculate v, convert units such as cm/s to m/s, or compare speeds of different waves. Always write the unit m/s, not m or Hz, and show substitution clearly.
What earns the marks
- State that wave speed is the distance travelled by a wave each second and is measured in metres per second (m/s).
- Recall and apply the wave equation v = f λ, where v is wave speed in m/s, f is frequency in Hz and λ is wavelength in m.
- Substitute numerical values correctly into v = f λ and calculate v, including converting cm or mm to m and Hz to s⁻¹ where needed.
- Describe a practical method to measure wave speed, such as timing a wave over a measured distance or using a ripple tank with a stopwatch.
- Compare wave speeds in different media or for different waves, linking a higher speed to greater distance travelled per second.
Common mistakes and how to put them right
Writing the unit as m or m/s² instead of m/s.
Put it right: Speed is distance per second, so the unit is metres per second, m/s.
Using wavelength in centimetres without converting to metres.
Put it right: Convert cm to m by dividing by 100 before substituting into v = f λ.
Rearranging v = f λ incorrectly, for example writing f = v λ.
Put it right: Divide both sides by λ to get f = v / λ, and by f to get λ = v / f.
Exam tips
- Write the equation v = f λ, then substitute values with units before calculating; this makes unit errors obvious.
- Check that your answer unit matches the question: if wavelength is in m and frequency in Hz, the speed is in m/s.
- For practical questions, name the measuring instruments and the distance timed, and repeat readings to reduce random error.
Try the lesson
The start of the Properties of waves: wave speed, v, in metres per second, m/s lesson, made from checked teaching notes for this specification point.
Have a go first
A wave travels 30 m in 6 s. What is the wave speed in m/s?
Listen
Wave speed, v, is the distance a wave crest travels each second, measured in metres per second (m/s). It links frequency f in hertz (Hz) and wavelength λ in metres (m) through the equation v = f λ. For example, a wave with f = 50 Hz and λ = 2 m has v = 50 × 2 = 100 m/s. You can also measure v directly: time a crest over a known distance, or use a ripple tank and stopwatch. In exams, you may calculate v, convert units such as cm/s to m/s, or compare speeds of different waves. Always write the unit m/s, not m or Hz, and show substitution clearly. A strong answer earns marks for these points. State that wave speed is the distance travelled by a wave each second and is measured in metres per second (m/s). Recall and apply the wave equation v = f λ, where v is wave speed in m/s, f is frequency in Hz and λ is wavelength in m. Substitute numerical values correctly into v = f λ and calculate v, including converting cm or mm to m and Hz to s⁻¹ where needed. Describe a practical method to measure wave speed, such as timing a wave over a measured distance or using a ripple tank with a stopwatch. A common slip: Writing the unit as m or m/s² instead of m/s. Instead, speed is distance per second, so the unit is metres per second, m/s. Exam tip: Write the equation v = f λ, then substitute values with units before calculating; this makes unit errors obvious.
See it
Key words
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wave speed
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frequency
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wavelength
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v = f λ
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See every definition
- wave speed
- The distance a wave crest travels each second, measured in metres per second (m/s).
- frequency
- Measured in hertz (Hz) and linked to wave speed and wavelength through the equation v = f λ.
- wavelength
- Measured in metres (m) and linked to wave speed and frequency through the equation v = f λ.
- v = f λ
- The wave equation linking wave speed v in m/s, frequency f in Hz and wavelength λ in m.
Label the diagram
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