The Compton Experiment

the x-ray apparatus used by Compton in his experiments

At its inception, the James B. Eads Hall at Washington University housed the Department of Physics. In 1923, the building housed Dr. Arthur Holly Compton’s lab, which sought to demonstrate the particle nature of light. At the time of Dr. Compton’s work, it was not widely accepted that light could act as both a wave and as a particle. Compton theorized that if an electron was hit with a photon, they would both change their paths, conserving energy and momentum, just as a particle would behave. 

The experiment in Eads Hall centered on an “x-ray apparatus” consisting of a lead box, a calcite crystal, and an electrometer. An x-ray would come out of the lead box, hit the calcite, and be detected by the electrometer. Using this setup, Compton and his team were able to detect changes in wavelength and x-ray induced ionized charge to conclude that the light was interacting with the electrons in the crystal as a particle rather than as a wave².

²Erik Henriksen; Arthur Compton and the mysteries of light. Physics Today 1 December 2022; 75 (12): 44–50. https://doi.org/10.1063/PT.3.5139