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Photoemission, also known as the photoelectric effect, is a phenomenon where electrons are emitted from a material when light shines on it. This occurs when the incident photons, particles of light, possess enough energy to overcome the binding energy of the electrons within the material. The minimum energy required to remove an electron from a specific material is called the work function.

The relationship between the energy of a photon and its frequency is given by Planck's equation, E = hf, where E is energy, h is Planck's constant, and f is frequency. If the energy of the incident photon (hf) is greater than the work function (Φ) of the material, then an electron can be emitted. The excess energy, hf - Φ, is then converted into the kinetic energy of the emitted electron. This kinetic energy can be expressed as ½mv², where m is the mass of the electron and v is its velocity.

The photoemission effect is dependent on the frequency of the incident light, not its intensity. If the frequency is below a certain threshold, no electrons will be emitted, regardless of how intense the light is. However, if the frequency is above the threshold, increasing the intensity of the light will increase the number of emitted electrons, but not their maximum kinetic energy.

This effect was famously explained by Albert Einstein in 1905, which provided strong evidence for the quantum nature of light, earning him the Nobel Prize in Physics in 1921. Photoemission has numerous practical applications, including in photomultipliers, solar cells, and image sensors in digital cameras.

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