Compton

Arthur Compton received a Doctorate in Physics from Princeton and then spent a year in Cambridge working under Ernest Rutherford investigating the properties of scattered gamma rays. In the early 1920's, at Washington University in St. Louis, he continued this work using x-rays instead of gamma rays.

After years of work he concluded that the scattering of x-rays by graphite lowered their energy. The x-rays were behaving like particles that transferred energy to the electrons of the graphite in a "collision". This provided experimental proof that electromagnetic radiation could exhibit the characteristics of particles as well as waves.Texts make the most of his confirmation of Einstein's quantum hypothesis. In fact the story is much less clear.

Compton experimented over seven years building on the work of well known people such as C. G. Barkla, D.C.H. Florance and J. A. Gray. Compton rejected one interpretation after another, misread his experimental data, then read it correctly, and in general struggled on his own. Einstein's name does not appear once in Compton's published papers. In the end Compton was nearly scooped in his discovery by Peter Debye, who by contrast was directly influenced by his knowledge of Einstein's light-quantum hypothesis.