Introduction to Young's Double-slit Experiment

Lenox Laser Young's Double Slit

The double slit experiment, thought to have been first performed by English scientist Thomas Young circa 1800, generally refers to an experiment in which light is allowed to diffract through slits which produces fringes, or wave-like interference patterns on an opposing screen.

A similar experiment was performed by Claus Jonsson of the University of Tubingen where beams of electrons showed similar interference patterns. The results of this experiment are often taken as evidence of the “wave-particle duality” predicted by quantum physics. (a.k.a. Englert-Greenberger duality)

In the case two pinholes are used instead of slits, as in the original Young’s experiment, hyperbolic fringes are observed. This is because the difference in paths traveled by the light from the two sources is a constant for a fringe which is the property of a hyperbola. If the two sources are placed on a line perpendicular to the screen, the shape of the interference fringes is circular as the individual paths traveled by light from the two sources are always equal for a given fringe.

It is little wonder that the experiment performed by Dr. Jonsson (Young’s Double Slit applied to the interference of single electrons) ranks first in the list of the top ten most beautiful experiments as chosen by the readers of Physics World magazine.

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