The phase of the wave goes through
in one wavelength in
So the wavelength
Similarly the phase goes through
in one period
is the angular frequency. It changes by
increases by 1 every cycle so
There is no reason to memorize these equations. They should be obvious.
Lets see how fast one of the peaks of the wave moves. This is called the phase velocity.
, there is a peak at
. This is the peak for which the argument of cosine is 0.
, the argument is zero when
If we compute the phase velocity by taking
, we get
In non-relativistic QM, we have
Jim Branson 2013-04-22