Schlieren Imaging of an Acoustic Guiding Wave in a Double-Slit Arrangement*

A double-slit acoustic wave diffraction pattern that guides the motion of small Styrofoam balls may serve as a visual analogue to the de Broglie-Bohm interpretation of electron double-slit diffraction. In our experiment, an ultrasonic sound wave impinges on a double slit creating a diffraction pattern. This diffraction pattern acts as a guide for Styrofoam balls, which are launched evenly into the slits. Schlieren Imaging is used to visualize both the acoustic wave and the particles’ paths. Our goal is to see if the resulting measured trajectories of the balls can be mapped onto the calculated trajectories of the electrons in the quantum mechanical description of double-slit diffraction. In the de Broglie-Bohm interpretation, the electron’s Bohmian trajectories are dictated by the Quantum potential. If the mapping is reasonably accurate, we hope to have provided an instructional resource for use in classrooms and educational laboratories. From the point of view of the history of physics, it is perhaps interesting to ponder de Broglie’s original “double solution” [1] where both the “particle” and wave existed separately, just as in our analogy, in distinction to our modern approach to quantum mechanics.

[1] Ann. de la Fond. Louis de Broglie, 12, 4, 1987, available at https://fondationlouisdebroglie.org/AFLB-classiques/aflb124p001.pdf