Albert Einstein’s explanation of the photoelectric effect described light, for the first time, in terms of photons rather than waves.
Each discrete photon’s energy corresponds to the frequency of the waves in the photon. This work led to the field of quantum mechanics. In 1921, Einstein earned a Nobel Prize for his work. (Photo: Wikimedia Commons/F Schmutzer)
(Courtesy of Wikimedia Commons / F Schmutzer)