(1905) Physics A model of light proposed by German-born mathematical physicist Albert Einstein (1879–1955).
Einstein developed the quantum ideas put forward by German theoretical physicist Max Karl Ernst Planck (1858–1947), and suggested that not only is electromagnetic radiation emitted in packets or quanta (called photons) but is transmitted and absorbed in such packets. Monochromatic radiation of frequency v behaves as if it comprises mutually independent energy quanta of magnitude hv, where h is Planck’s constant. Einstein used this idea in discussion of the photoelectric effect, in which he assumed that a photon transfers all its energy to a single electron and the energy transfer by one light quantum is independent of the presence of other light quanta. See PHOTOELECTRIC EFFECT.
J Thewlis, ed., Encyclopaedic Dictionary of Physics (New York, Oxford and London, 1962)
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