Walther Friedrich coauthored the experimental observation of X-ray diffraction by a crystal with Paul Knipping and Max von Laue. A beam transmitted through the sample produced separated spots on a photographic plate. Their geometry connected the periodic structure of the crystal with constructive interference of the scattered radiation. The apparatus turned a proposed wave test into an observable pattern, providing a method for investigating matter on atomic length scales.[ref]
Interferenz-Erscheinungen bei Röntgenstrahlen by Walther Friedrich, Paul Knipping and Max von Laue. 1912 report, experimental arrangement and diffraction photographs
A physicist.[ref]
https://www.bbaw.de/die-akademie/akademie-historische-aspekte/mitglieder-historisch/historisches-mitglied-walter-friedrich-804. Independent biographical identity and professional specialization
Portrait of Walther Friedrich
. Source. 
New to topics? Read the docs here!