AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Properties of waves: wave speed = frequency × wavelength
This statement expresses the wave equation in words: wave speed equals frequency multiplied by wavelength.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 12 of 18
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
This statement expresses the wave equation in words: wave speed equals frequency multiplied by wavelength. Wave speed is the distance a wave travels each second, measured in metres per second (m/s). Frequency is how many complete waves pass a point each second, measured in hertz (Hz). Wavelength is the distance between two identical points on neighbouring waves, such as trough to trough, measured in metres (m). For instance, a wave with frequency 50 Hz and wavelength 2 m travels at 50 × 2 = 100 m/s. The word equation is useful because it shows the relationship directly: increasing frequency or wavelength increases wave speed, provided the other quantity stays constant.
What earns the marks
- Identify wave speed as the distance travelled per second by a wave, measured in m/s.
- Identify frequency as the number of complete waves per second, measured in Hz, and wavelength as the distance between equivalent points on consecutive waves, measured in m.
- Use the word equation wave speed = frequency × wavelength to calculate one quantity when the other two are known.
- Explain that for a given wave speed, frequency and wavelength are inversely proportional, so a higher frequency means a shorter wavelength.
- Apply the relationship to real waves, such as calculating the speed of a water wave from its frequency and wavelength.
Common mistakes and how to put them right
Adding frequency and wavelength instead of multiplying them.
Put it right: The relationship is multiplicative, so use frequency × wavelength.
Mixing units, such as using frequency in kHz with wavelength in m.
Put it right: Convert frequency to Hz first.
Thinking wavelength is the height of a wave.
Put it right: Wavelength is a horizontal distance between equivalent points, while amplitude is the height from the middle to a crest.
Exam tips
- Underline the quantities given in the question and the quantity required before choosing the calculation.
- Show the word equation, then substitute numbers with units, then calculate and state the unit.
- If the answer seems unrealistic, check for a unit conversion error, especially between cm and m or kHz and Hz.
Try the lesson
The start of the Properties of waves: wave speed = frequency × wavelength lesson, made from checked teaching notes for this specification point.
Have a go first
A water wave has a frequency of 4 Hz and a wavelength of 3 m. Using wave speed = frequency × wavelength, what is the speed of the wave?
Listen
This statement expresses the wave equation in words: wave speed equals frequency multiplied by wavelength. Wave speed is the distance a wave travels each second, measured in metres per second (m/s). Frequency is how many complete waves pass a point each second, measured in hertz (Hz). Wavelength is the distance between two identical points on neighbouring waves, such as trough to trough, measured in metres (m). For instance, a wave with frequency 50 Hz and wavelength 2 m travels at 50 × 2 = 100 m/s. The word equation is useful because it shows the relationship directly: increasing frequency or wavelength increases wave speed, provided the other quantity stays constant. A strong answer earns marks for these points. Identify wave speed as the distance travelled per second by a wave, measured in m/s. Identify frequency as the number of complete waves per second, measured in Hz, and wavelength as the distance between equivalent points on consecutive waves, measured in m. Use the word equation wave speed = frequency × wavelength to calculate one quantity when the other two are known. Explain that for a given wave speed, frequency and wavelength are inversely proportional, so a higher frequency means a shorter wavelength. Exam tip: Underline the quantities given in the question and the quantity required before choosing the calculation.
See it
Key words
Say what each word means before you turn the card.
Wave speed
Try answering aloud or in your head before turning the card.
Frequency
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Wavelength
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Wave equation
Try answering aloud or in your head before turning the card.
See every definition
- Wave speed
- The distance a wave travels each second, measured in metres per second (m/s).
- Frequency
- How many complete waves pass a point each second, measured in hertz (Hz).
- Wavelength
- The distance between two identical points on neighbouring waves, such as trough to trough, measured in metres (m).
- Wave equation
- Wave speed equals frequency multiplied by wavelength, showing the relationship directly.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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