Phase Velocity: What Does it Tell Us About Waves?

[manimaran1605]

What is phase velocity? I know it is defined as v=ω/κ
But what does this phase velocity tells about the wave? Does it means the velocity of wave?

 

[sophiecentaur]

It simply tells you the speed at which the peaks (etc.) of a continuous, unmodulated wave will progress.

This is not a quantity that is easy to measure when you need to involve many cycles of the wave from A to B. We need to modulate the beam, normally - for measuring the speeds of em waves (except the longer wavelengths, where we can measure the frequency accurately and also find the wavelength easily). For light, we need to look at the group velocity (of a light pulse, for instance).