Editing Capillary wave (section)

===Capillary waves, proper===
The dispersion relation for capillary waves is

:<math>
\omega^2=\frac{\sigma}{\rho+\rho'}\, |k|^3,</math>
where <math>\omega</math> is the [[angular frequency]], <math>\sigma</math> the [[surface tension]], <math>\rho</math> the [[density]] of the 
heavier fluid, <math>\rho'</math> the density of the lighter fluid and <math>k</math> the [[wavenumber]]. The [[wavelength]] is 
<math>
\lambda=\frac{2 \pi}{k}.</math>
For the boundary between fluid and vacuum (free surface), the dispersion relation reduces to
:<math>
\omega^2=\frac{\sigma}{\rho}\, |k|^3.</math>