Damping of Cylindrical Propagating Capillary Waves on Monolayer-Covered Surfaces

Cylindrical propagating capillary waves are generated by an electrical “point source” and detected with a reflected laser beam. The surface properties of monolayers of soluble (Triton X-100) and insoluble (n-dodecyl p-toluenesulfonate) surfactant solutions were investigated through both propagating plane and cylindrical capillary waves. We found that the values of measured damping coefficients and wavelengths of plane waves are equal to those of cylindrical waves. Computed values of the surface properties, elastic modulus t and surface pressure II, for both waves are obtained and found to be identical. Our results show that even though plane and cylindrical transverse waves possess different geometries, they can be used to obtain surface dilational properties accurately. Also, the dispersion equation for propagating cylindrical waves is explicitly derived.