fázissebesség

Fázissebesség refers to the speed at which the phase of a wave propagates in space. It is a fundamental concept in wave physics, particularly when dealing with electromagnetic waves, light, and sound. Mathematically, it is defined as the ratio of the angular frequency (ω) of the wave to its wave number (k), expressed as v_p = ω/k.

The phase velocity indicates how fast a point of constant phase, such as a wave crest or trough, travels. It is important to note that phase velocity does not necessarily represent the speed at which energy or information is transmitted. In many media, the phase velocity can be greater than the speed of light in a vacuum (c), which is consistent with the fact that it does not violate causality.

The value of the phase velocity depends on the properties of the medium through which the wave is traveling and the frequency of the wave. In some cases, the medium's properties vary with frequency, leading to a phenomenon known as dispersion. In a dispersive medium, different frequency components of a wave travel at different phase velocities, which can cause the waveform to distort over time. The speed of energy propagation in such media is described by the group velocity, which is generally different from the phase velocity.