High Quality Content by WIKIPEDIA articles! The phase velocity (or phase speed) of a wave is the rate at which the phase of the wave propagates in space. This is the speed at which the phase of any one frequency component of the wave travels. For such a component, any given phase of the wave (for example, the crest) will appear to travel at the phase velocity. The phase speed is given in terms of the wavelength (lambda) and period T as v_mathrm{p} = frac{lambda}{T}.