The Double Slit Experiment
Hundreds of years before the double slit experiment, thinkers and scientists argued about the nature of light. In the 17th century, French scientist and astronomer Pierre Gassendi and Sir Isaac Newton argued that light propagates through space as a steady stream of particles. In the early 1760s Leonhard Euler maintained that light was a wave propagating through aether. Euler argued that if the sun were constantly emitting particles it would be rapidly decreasing in size. The theory behind Thomas Young's experiment is straightforward. Unlike particles, waves obey the mathematical principle of superposition and also unlike particles, waves have the potential to interfere with one another. Young passed monochromatic light through two slits in an otherwise opaque partition onto a dark screen. When light was allowed to pass through only one slit at a time the light was distributed on the screen evenly. When light was allowed to pass through both slits at the same time he observed an i...