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The Faraday Wave Experiment

 

You fill a container with a liquid and shake it vertically at a fixed frequency and amplitude. That is the experiment M. Faraday  presented in an appendix to an article in the Philosophical Transactions of the Royal Society London in 1831  [5].

In this article "on a peculiar class of acoustical Figures" Faraday writes about how, by choosing the right combination of liquid, frequency, and amplitude, very beautiful square patterns of standing waves can be seen on the surface of the liquid.

The experiments I have done with this set-up were to trace small particles floating on the surface, and thus measure diffusion on the surface waves. When you look at the tracks of the particles, they appear, in striking contrast to the surface waves, to be quite irregular and random. It would be interesting to understand how this random motion on the surface can be induced by the ordered motion in the bulk indicated by the wave patterns.

  figure535
Figure 2.1: The two appearances of Faraday waves. Left: Square standing waves. The black disc to the right in the image was used to measure the amplitude of the vibrations of the container. Right: Tracks of particles floating on the surface.

The set-up I have been working on was originally created by Bo Christiansen and Mogens T. Levinsen. It was later modified for these measurements by Walter Goldburg, Mogens T. Levinsen and myself.





sparre@cats.nbi.dk