7.1.4—The definitions of speed, frequency and wavelength, the wave equation v = f

For a progressive wave, v=fλ, where v is speed, f frequency and λ wavelength. The relation follows because one wavelength travels in one period.

Use frequency in hertz and wavelength in metres. In a fixed medium, changing frequency generally changes wavelength so that the speed remains set by the medium.

A 250 Hz sound wave with wavelength 1.36 m travels at 340 m s⁻¹.

Frequency is set by the source, while speed is not automatically equal to frequency; do not confuse v with particle oscillation speed.