Image »Phase velocity of a wave crest« download
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Phase velocity \( v_{\text p} \) of any point A on the wave, is the velocity with which this point propagates from A to B. Also drawn in is the wavelength \(\lambda\). This is here the distance between A and B. The phase velocity is given by the distance per time, so in this case wavelength \(\lambda\) per period \(T\):
\[ v_{\text p} ~=~ \frac{\lambda}{T} \]
