Noncontact Measurement of Surface Tension by Ripplon Light Scattering Spectroscopy

Authors:
  • AOAtsumi Ozawa
    Atsumi Ozawa
  • AMAkiko Minamisawa
    Akiko Minamisawa
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Abstract
A new method of rapid and non-contact surface tension measurement based on the ripplon light scattering technique is described. A light beam from a cw-YAG laser with 100 mW output was focused on the surface in a small spot of a diameter comparable to the coherent length of ripplon. A very intense signal of the ripplon light scattering was thus obtained and the time required for the measurement was successfully reduced to ∼5 s. High spatial resolution was also obtained using the focused laser beam. The dispersion relation of ripplon on a pure water surface was measured over a wide frequency range from 10 kHz up to 1 MHz, and the surface tension was determined to be within an accuracy of 1%. The result of surface tension measurement obtained for a water/ethanol mixture is also demonstrated.