Phase velocity and group velocity are two very important concepts in physics. ... The group velocity is the velocity of the wave with lower frequency, but the phase velocity is the velocity of the wave with higher frequency. Phase Velocity The phase velocity of a wave is the rate at which the phase of the wave propagates in space. This is the velocity 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 velocity is given in terms of the wavelength λ (lambda) and time period T as Equivalently, in terms of the wave's angular frequency ω , which specifies angular change per unit of time, and wavenumber (or angular wave number) k , which represents the proportionality between the angular frequency ω ...
Optics for Optometry