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| This equation is an application of the conservation of energy. It states that the energy of a photon incident upon the surface of a metal is used partly in freeing the least bound electron (using up energy F) , the remainder being given to the kinetic energy Ek of the ejected electron. The surprise was that one electron required one 'quantum' of electromagnetic radiation (above a threshold frequency), to release it. These quanta became known as 'Photons' and provided evidence for the particulate nature of 'light'. |