Photoelectric Effect

The Photoelectric Effect

Definition: It is the emission of electrons from a metal surface under the illumination of a suitable radiation.

The photoelectric effect is the phenomenon whereby electrons are emitted from a surface (usually metallic) upon the exposure to and absorption of electromagnetic radiation, such as visible light, that is above the threshold frequency. This is because electrons cannot get enough energy to overcome their atomic bonding. The photoelectric effect furthered wave particle duality, whereby physical systems (i.e.: photons in this case) can display both wave - like and particle - like properties and behaviours, a concept used by the creators of quantum mechanics. It was explained mathematically by Einstein, utilising work in quantum mechanics, and was developed by people like Max Planck.

The photoelectric effect was not just an immediate discovery with a definite drawn conclusion. It involved many years of research, experimentation and debating. In 1887, Heinrich Hertz first discovered the concept of the photoelectric effect when he was investigating the production and reception of electromagnetic waves. From this experiment, after several years it was determined that when light shines on a metal surface, the surface emits electrons, for example, it can start a current in a circuit just by shining a light on a metal plate. In 1899, Joseph John Thompson investigated ultraviolet light in cathode ray tubes and deduced that cathode rays existed of negatively charged particles, which he called corpuscles (later called electrons). In 1901, Nikola Tesla received the patent US68597 (Apparatus for the Utilisation of Radiant Energy) that describes radiation charging and discharging conductors (metal plates) by "radiant energy". Tesla used this effect to charge a capacitator with energy by means of a conductive plate. These devices were referred to as "photoelectric alternating stepping motors". In 1905, Einstein published the theory that successfully explained the photoelectric effect. He said that light is composed of discrete particles of energy, or quanta, called photons, the energy of each photon being proportional to its frequency according to the equation E = h * Φ, where E is the energy, h is Planck's constant, and Φ is the frequency. Each photoelectron ejected is as a

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