Noun
English Wikipedia has an article on:phase velocityWikipedia
phase velocity
(physics) The velocity of propagation of a pure sine wave of infinite extent and infinitesimal amplitude.
A homogeneous and harmonic plane wave is a constant-frequency wave whose wavefronts (surfaces of constant phase ) are infinite parallel planes of constant peak-to-peak amplitude normal to the phase velocity vector. Source: Internet
For example, this occurs in most glasses at X-ray frequencies. citation However, the phase velocity of a wave corresponds to the propagation speed of a theoretical single-frequency (purely monochromatic ) component of the wave at that frequency. Source: Internet
In a given medium, the frequency is some function ω(k) of the wave number, so in general, the phase velocity and the group velocity depend on the frequency and on the medium. Source: Internet
In effect, the individual waves (which travel with the phase velocity) escape from the wave packet (which travels with the group velocity). Source: Internet
At the boundary between the media, the wave's phase velocity is altered, usually causing a change in direction. Source: Internet
Due to the change of medium, the phase velocity of the wave is changed but its frequency remains constant. Source: Internet