AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Properties of waves: wavelength, λ, in metres, m
Wavelength, λ, is the distance between two identical points on consecutive waves, such as crest to crest or trough to trough, measured in metres (m).
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 14 of 18
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Wavelength, λ, is the distance between two identical points on consecutive waves, such as crest to crest or trough to trough, measured in metres (m). It is the spatial period of a wave: a longer wavelength means fewer waves pass a point each second if speed is constant. You can measure λ on a displacement–distance graph by reading the horizontal distance for one complete cycle, or in a ripple tank by measuring across several wavelengths and dividing. Wavelength links to frequency and wave speed through v = f λ. In exams, you may read λ from a graph, convert cm to m, or calculate λ using λ = v / f. Always include the unit m.
What earns the marks
- Define wavelength as the distance between two consecutive identical points on a wave, such as crest to crest or trough to trough.
- State that wavelength is measured in metres (m) and convert measurements from cm or mm to m when required.
- Read wavelength from a displacement–distance graph by identifying one complete wave cycle and measuring its horizontal length.
- Use the equation λ = v / f to calculate wavelength when wave speed and frequency are known.
- Describe a practical method to measure wavelength, such as measuring across several waves in a ripple tank and dividing by the number of waves.
Common mistakes and how to put them right
Measuring from crest to trough instead of crest to crest.
Put it right: Wavelength is the distance between identical points on consecutive waves, so use crest to crest or trough to trough.
Forgetting to convert centimetres to metres.
Put it right: Divide a measurement in cm by 100 to obtain metres before using it in calculations.
Confusing wavelength with amplitude.
Put it right: Amplitude is the maximum displacement from the rest position, while wavelength is a horizontal distance along the wave.
Exam tips
- On a graph, mark one full cycle from crest to crest and read the horizontal distance carefully using the scale.
- When measuring several wavelengths, divide the total distance by the number of complete waves to reduce percentage error.
- Always write the unit m after a wavelength value, and check that your calculation uses v in m/s and f in Hz.
Try the lesson
The start of the Properties of waves: wavelength, λ, in metres, m lesson, made from checked teaching notes for this specification point.
Have a go first
A wave has a wavelength of 3 m. What does this value tell you about the wave?
Listen
Wavelength, λ, is the distance between two identical points on consecutive waves, such as crest to crest or trough to trough, measured in metres (m). It is the spatial period of a wave: a longer wavelength means fewer waves pass a point each second if speed is constant. You can measure λ on a displacement–distance graph by reading the horizontal distance for one complete cycle, or in a ripple tank by measuring across several wavelengths and dividing. Wavelength links to frequency and wave speed through v = f λ. In exams, you may read λ from a graph, convert cm to m, or calculate λ using λ = v / f. Always include the unit m. A strong answer earns marks for these points. Define wavelength as the distance between two consecutive identical points on a wave, such as crest to crest or trough to trough. State that wavelength is measured in metres (m) and convert measurements from cm or mm to m when required. Read wavelength from a displacement–distance graph by identifying one complete wave cycle and measuring its horizontal length. Use the equation λ = v / f to calculate wavelength when wave speed and frequency are known. A common slip: Measuring from crest to trough instead of crest to crest. Instead, wavelength is the distance between identical points on consecutive waves, so use crest to crest or trough to trough. Exam tip: On a graph, mark one full cycle from crest to crest and read the horizontal distance carefully using the scale.
See it
Key words
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wavelength
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displacement–distance graph
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ripple tank
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λ = v / f
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See every definition
- wavelength
- The distance between two identical points on consecutive waves, such as crest to crest or trough to trough, measured in metres (m).
- displacement–distance graph
- A graph on which wavelength is read by identifying one complete wave cycle and measuring its horizontal length.
- ripple tank
- A practical arrangement in which wavelength is measured across several wavelengths and divided by the number of waves.
- λ = v / f
- The equation used to calculate wavelength when wave speed and frequency are known.
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