fotokatodeissa

Fotokatodeissa, also known as photocathodes, are a crucial component in devices that detect light. They are a type of electrode that emits electrons when exposed to electromagnetic radiation, typically in the visible or ultraviolet spectrum. This phenomenon is known as the photoelectric effect.

The material used for a photocathode is chosen for its low work function, meaning it requires minimal energy for electrons to escape its surface. Common materials include alkali metals like cesium, antimony, and their compounds, often deposited as thin films on a transparent substrate. The specific composition of the photocathode determines its spectral sensitivity, or the range of wavelengths of light it can effectively convert into electrons.

When photons of sufficient energy strike the photocathode, they transfer their energy to electrons within the material. If this energy exceeds the work function, the electrons are ejected from the surface. These emitted electrons, called photoelectrons, are then accelerated towards an anode, creating an electrical current that can be measured. This current is proportional to the intensity of the incident light.

Fotokatodeissa are fundamental to the operation of various light-sensitive devices. They are found in photomultiplier tubes (PMTs), used for detecting very faint light signals, and in image intensifier tubes, which amplify low light levels. They also play a role in some types of photodetectors and vacuum phototubes. The efficiency of a photocathode, its quantum efficiency, refers to the ratio of emitted photoelectrons to incident photons.