Phyics of Wave Group Velocities in Metrology for Dispersion Media

Phase and group velocities of wave are most frequently used in the research of physical processes and phenomena in dispersion media. The difference existing between phase velocities of ideal harmonic waves and real non-monochromatic waves comes into conflict with their physical interpretation, that sometimes brings some additional errors both in theoretical investigations and the results of physical measurements. The concepts developed at the beginning of the 20th century have not been properly estimated and now they need to be specified and revised.