Young's interference experiment

This is a placeholder entry. Young's interference experiment is the 1801 double-slit demonstration by Thomas Young in which coherent light passing through two parallel slits produced a pattern of bright and dark fringes on a screen, establishing the wave nature of light against Newton's corpuscular theory. The fringe spacing λL/d (where L is the screen distance and d the slit separation) matched the wave-theory prediction and could not be accounted for by any particle model.

The full quantitative treatment appears in §09.7 interference (constructive-interference, destructive-interference, coherence-length) and §09.8 diffraction-and-the-double-slit (see the double-slit-diffraction glossary entry). The same experimental setup, performed a century and a quarter later with electrons, photons one at a time, and heavy molecules, became the defining illustration of wave–particle duality in quantum mechanics.