Used with permission of Maiken Naylor, University at Buffalo, Buffalo, NY, USA, http://ublib.buffalo.edu/libraries/units/sel/exhibits/stamps

Albert Einstein's (1879-1955) name is associated with the general and special theories of relativity, but his explanation of the photoelectric effect, a phenomenon which could not be be accounted for by electromagnetic wave theory, won him the Nobel prize in physics. He proposed a corpuscular model of radiation as the photoelectric mechanism. Light travels in quanta (or photons) and must be of a certain threshhold energy (or color) to cause the emission of electrons from a given surface, while its intensity determines only the number of electrons so released. This German stamp shows electrons escaping at random angles while light strikes the surface.
Einstein's law E=mc2 is shown on Nicaragua Scott 879 and features a stylized mushroom cloud generally associated with a nuclear bomb explosion. Inside the mushroom cap appears a beryllium atom with four electrons orbiting a nucleus of four protons and five neutrons. "Beryllium is a highly efficient generator of neutrons when bombarded with alpha particles. It may serve as a source of neutrons to initiate the nuclear fission within the fuel nucleus of a reactor." (Gmelin Handbook Be Suppl.vol. A1 p.124). At the base of the mushroom are roiling, churning clouds of debris as seen on actual photos of nuclear events. However, front and center in the picture is a prone white-draped figure being irradiated from upper left, watched by a technician behind a window to the right. This peaceful application of nuclear energy somewhat mitigates the stark symbolism of the mushroom cloud. The image of Einstein transcends national boundaries; here are but a few impressions of his somber countenance.