Direct measurement of the attenuation of capillary waves by laser interferometry: Noncontact determination of viscosity

The determination of viscosity from the damping of capillary waves has been of great interest, as it affords the possibility of measuring viscosity without contact with the fluid. Here we describe a noncontact method for precision measurement of the amplitude of capillary waves on fluids. The technique utilizes a miniature laser interferometer to map the wave profile with a resolution of about 10 nm, We use this technique to obtain the dispersion and attenuation of capillary waves on water as a test case. Furthermore, the attenuation data is used to obtain the viscosity of water as a function of temperature. (C) 2001 American Institute of Physics.