Translations:Phase velocity/22/en

The term on the left represents the velocity of propagation, subject to the condition of constant phase. Choose any point on the wave profile - for example, the crest of the wave. As the wave moves through space, the displacement u of the crest remains constant. Because the only variable in the sinusoidal wave function is the phase, it too must be constant. That is, the phase is fixed at a value producing the constant displacement u at the chosen point. The point moves along with the profile at velocity v, and so does the constant phase condition.