Measurement of liquid surface properties using a He-Ne laser

The surface tension, viscosity, and damping coefficient of surface waves on a liquid sample have been determined by observing the diffraction of an optical beam. To achieve high accuracy, a He-Ne laser having a high brightness and coherence was used as a light source. Experiments illustrating and verifying the techniques are described.Values of the surface tension for different samples have been measured with a standard deviation of less than ±0.6% for frequencies of the ripple motion ranging from 500 to 3 000 Hz over the temperature range 20–45°C. The viscosity and damping coefficient of water were measured for frequencies in the range 600–1500 Hz. The values obtained agree with those available from the literature.