In all cases of wave motion the wave-length is connected with the velocity of propagation of the radiation by the relation v=nX, where n is the frequency of the oscillations and X is the wave-length.
The velocity of propagation of electric waves is the same as that of light, viz., about moo million feet, or 300 million metres, per second.
If we omitted it we should have to assume this, and equation (6) would give us the velocity of propagation if the assumption were justified.
They found that the velocity of propagation of different musical sounds was the same.
Hence sound rays, in passing from one medium into another, are bent in towards the normal, or the reverse, according as the velocity of propagation in the former exceeds or falls short of that in the latter.