Editing Albert Einstein (section)

==== Wave–particle duality ====
[[File:Albert Einstein 1921 (re-cropped).jpg|thumb|upright|Einstein in 1921, by [[Harris & Ewing]] studio]]
Although the patent office promoted Einstein to Technical Examiner Second Class in 1906, he had not given up on academia. In 1908, he became a ''[[Privatdozent]]'' at the University of Bern.{{Sfnp|Pais|1982|p=522}} In "''Über die Entwicklung unserer Anschauungen über das Wesen und die Konstitution der Strahlung''" ("[[s:Translation:The Development of Our Views on the Composition and Essence of Radiation|The Development of our Views on the Composition and Essence of Radiation]]"), on the [[quantization (physics)|quantization]] of light, and in an earlier 1909 paper, Einstein showed that Max Planck's energy quanta must have well-defined [[momentum|momenta]] and act in some respects as independent, [[point particle|point-like particles]]. This paper introduced the ''photon'' concept and inspired the notion of [[wave–particle duality]] in quantum mechanics. Einstein saw this wave–particle duality in radiation as concrete evidence for his conviction that physics needed a new, unified foundation.