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Unformatted text preview: Einstein used the concept of the photon to explain the results of an experimental phenomenon called the photoelectric effect . The photoelectric effect was the observation that when light was shone on a metal surface, the surface emitted electrons. Thus, it was possible to generate a current in a circuit just by shining light on a metal plate. The ejection of electrons from a metal surface could be explained by the idea of light as waves. Since waves transport energy, a wave of light could transfer enough energy to knock electrons out of atoms in the metal when it hit the metal surface. However, light as purely waves could not explain the other experimental observations of photoelectric effect. Electrons were emitted only when the frequency of the light was above a certain minimum value (called the threshold frequency ) that was characteristic for each metal. Below the threshold frequency for the metal, no electrons were emitted, regardless of the intensity (or brightness) of the light shone on the metal. When the frequency of the light was greater than the threshold frequency, experimental measurements demonstrated that the kinetic energy of the individual ejected electrons was proportional to the frequency, rather than the intensity of the light. electrons was proportional to the frequency, rather than the intensity of the light....
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