Phase Velocity

Phase velocity is the speed at which a particular point of a wave's oscillation, such as a crest or trough, moves through space. Imagine a wave on a string; the crest travels along the string at a certain speed. This speed is the phase velocity. It's important to note that phase velocity describes the movement of a specific phase point within the wave, not necessarily how quickly energy or information is transported. In some cases, phase velocity can exceed the speed of light, but this does not violate physics because no usable signal travels this fast.