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Wave speed calculator

GCSEA-level Waves

The wave speed is the frequency multiplied by the wavelength.

v = f λ

This free calculator is for GCSE and A-level physics. Choose the quantity you want to find, enter the other values with their units, and it shows the working in the layout used in exams, with the answer to the number of significant figures you choose. The values shown are an example. Change them to your own.

Quantity to find

343 m/s

Working

  1. Write the equation
    v = f λ
  2. Substitute the values
    v = 440 × 0.78
  3. Calculate
    v = 343.2 m/s
  4. Give the answer to 3 significant figures
    v = 343 m/s

Worked example

Find v, the wave speed. Given: frequency f = 440 Hz; wavelength λ = 0.780 m.

  1. Write the equation
    v = f λ
  2. Substitute the values
    v = 440 × 0.78
  3. Calculate
    v = 343.2 m/s
  4. Give the answer to 3 significant figures
    v = 343 m/s

Symbols and units

SymbolQuantitySI unit
vWave speedm/s
fFrequencyHz
λWavelengthm

Wave speed: rearranged

  • To find wave speed: v = f λ
  • To find frequency: f = v / λ
  • To find wavelength: λ = v / f

Exam tip

Frequency is in hertz and wavelength in metres. Radio and light questions often give wavelength in nm or cm.

Common questions

What is the formula for wave speed?

The equation is v = f λ, where v is the wave speed (m/s); f is the frequency (Hz); λ is the wavelength (m).

What units should I use for wave speed?

In SI units: wave speed in m/s, frequency in Hz, wavelength in m. The calculator also accepts common alternatives such as kilometres, grams or minutes, and converts them for you.

How do I rearrange v = f λ?

Rearranging gives these forms: to find wave speed: v = f λ. to find frequency: f = v / λ. to find wavelength: λ = v / f.

Practise wave speed questions

Press the button for a question with random numbers. Work it out on paper first, then type your answer.

Related

Read the full explanation on the Wave speed formula page. More waves equations: Frequency and time period, Magnification, Refractive index, Snell’s law, Critical angle, Double-slit fringe spacing, Diffraction grating, Intensity. See the full list on the physics equation calculator page.