Search results
Results from the WOW.Com Content Network
A phototube or photoelectric cell is a type of gas-filled or vacuum tube that is sensitive to light. Such a tube is more correctly called a 'photoemissive cell' to distinguish it from photovoltaic or photoconductive cells. Phototubes were previously more widely used but are now replaced in many applications by solid state photodetectors.
The photoelectric effect is the emission of electrons from a material caused by electromagnetic radiation such as ultraviolet light. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, solid state, and quantum chemistry to draw inferences about the properties of atoms, molecules and ...
The photodetector contains three photodiodes, visible in the photo (in center). Photodetectors , also called photosensors , are sensors of light or other electromagnetic radiation . [ 1 ] There are a wide variety of photodetectors which may be classified by mechanism of detection, such as photoelectric or photochemical effects, or by various ...
The quantity is proportional to the energy deposited by the ionizing particle. These can be directed to the photocathode of a photomultiplier tube which emits at most one electron for each arriving photon due to the photoelectric effect. This group of primary electrons is electrostatically accelerated and focused by an electrical potential so ...
Although a plain metallic cathode will exhibit photoelectric properties, the specialized coating greatly increases the effect. A photocathode usually consists of alkali metals with very low work functions. The coating releases electrons much more readily than the underlying metal, allowing it to detect the low-energy photons in infrared radiation.
Historically, the photoelectric effect is associated with Albert Einstein, who relied upon the phenomenon to establish the fundamental principle of quantum mechanics in 1905, [4] an accomplishment for which Einstein received the 1921 Nobel Prize. It is worthwhile to note that Heinrich Hertz, working 18 years earlier, had not recognized that the ...
The technical term PSD was first used in a 1957 publication by J.T. Wallmark for lateral photoelectric effect used for local measurements. On a laminar semiconductor, a so-called PIN diode is exposed to a tiny spot of light. This exposure causes a change in local resistance and thus electron flow in four electrodes.
This formula defines the photoelectric effect. Not every photon which encounters an atom or ion will photoionize it. The probability of photoionization is related to the photoionization cross-section, which depends on the energy of the photon and the target being considered. For photon energies below the ionization threshold, the ...