I have a question on "k" of an armonic simple movement.
If we take the equation of a wave, this is:
\frac {\partial \psi (x,t)}{\partial x^2} = \frac 1 v^2 \frac {\partial^2 \psi (x,t)}{\partial t^2}
And this, if I'm not wrong, must to satisfy the independent of time Helmholtz...