fotoemissioon

Fotoemissioon, also known as the photoelectric effect, is the emission of electrons or other charge carriers when electromagnetic radiation, such as light, hits a material. This phenomenon was first observed by Heinrich Hertz in 1887. Albert Einstein provided a theoretical explanation for the photoelectric effect in 1905, for which he was awarded the Nobel Prize in Physics in 1921.

The photoelectric effect occurs when photons of sufficient energy strike a material. If a photon's energy is greater than or equal to the work function of the material (the minimum energy required to remove an electron), an electron can be ejected. The work function is a characteristic property of the material. The kinetic energy of the emitted electron is equal to the energy of the incident photon minus the work function. This means that higher energy photons will result in electrons with higher kinetic energy. The intensity of the light, meaning the number of photons, affects the number of emitted electrons, but not their individual kinetic energies.

The photoelectric effect has important applications. It is used in photomultiplier tubes, which are highly sensitive detectors of light, and in solar cells, where light energy is converted into electrical energy. It also plays a role in various scientific instruments, such as spectrophotometers and image sensors in digital cameras. The understanding of the photoelectric effect was a crucial step in the development of quantum mechanics, demonstrating the particle-like nature of light.