The wave speed is the distance a wave travels each second. It is measured in metres per second (m/s). For any wave, the speed depends on the frequency and the wavelength:
wave speed (m/s) = frequency (Hz) × wavelength (m)
A wave with a frequency of 5 Hz and a wavelength of 2 m has a speed of 5 × 2 = 10 m/s. The equation can be rearranged. Frequency = wave speed ÷ wavelength, and wavelength = wave speed ÷ frequency.
In a given medium the wave speed is constant, so frequency and wavelength are linked. If the frequency doubles, the wavelength is halved. For example, a wave with a frequency of 20 Hz and a wavelength of 3 m has a speed of 60 m/s. At the same speed, a frequency of 40 Hz gives a wavelength of 1.5 m.