Use the formula: wavelength = wave speed ÷ frequency
Write it as: λ = v / f
Measure wave speed in meters per second (m/s)
Measure frequency in hertz (Hz)
Divide the wave speed by the frequency
The result is the wavelength in meters
For light in a vacuum, use: λ = c / f
For sound, use the speed of sound in the medium
If the period is known, use: wavelength = wave speed × period
Write it as: λ = v × T