Universal wave equation

The universal wave equation is

`v = f lambda`.

propagation speed (`v`)
the speed of the wave, measured in metres per second (m/s)
frequency (`f`)
the number of cycles completed in one second, measured in hertz (Hz)
wavelength (`lambda`)
the length of one cycle in the wave, measured in metres (m)

We also have a few other equations for dealing with period:

`f = N/(Delta t) qquad and qquad T = (Delta t)/N qquad and qquad f = 1/T`.

number of cycles (`N`)
the number of cycles completed during a time interval (unitless)
time interval (`Delta t`)
a specific duration of time, measured in seconds (s)
period (`T`)
the time it takes for one cycle to be completed, measured in seconds (s); wavelength is the spatial length, period is the temporal length