In
physics
Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...
, the Dember effect is when the
electron
The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...
current
Currents, Current or The Current may refer to:
Science and technology
* Current (fluid), the flow of a liquid or a gas
** Air current, a flow of air
** Ocean current, a current in the ocean
*** Rip current, a kind of water current
** Current (hydr ...
from a
cathode
A cathode is the electrode from which a conventional current leaves a polarized electrical device such as a lead-acid battery. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. Conventional curren ...
subjected to both illumination and a simultaneous electron bombardment is greater than the sum of the
photoelectric
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 physic ...
current
and the secondary emission current
.
History
Discovered by (1882–1943) in 1925, this effect is due to the sum of the excitations of an electron by two means: photonic illumination and electron bombardment (i.e. the sum of the two excitations extracts the electron). In Dember’s initial study, he referred only to metals; however, more complex materials have been analyzed since then.
Photoelectric effect
The
photoelectric effect
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 physi ...
due to the illumination of the metallic surface extracts electrons (if the energy of the photon is greater than the extraction work) and excites the electrons which the photons don’t have the energy to extract.
In a similar process, the electron bombardment of the metal both extracts and excites electrons inside the metal.
:
If one considers
a constant and increases
, it can be observed that
has a maximum of about 150 times
.
On the other hand, considering
a constant and increasing the intensity of the illumination
the
, supplementary current, tends to saturate. This is due to the usage in the photoelectric effect of all the electrons excited (sufficiently) by the primary electrons of
.
See also
*
Anomalous photovoltaic effect The anomalous photovoltaic effect (APE) is a type of a photovoltaic effect which occurs in certain semiconductors and insulators. The "anomalous" refers to those cases where the photovoltage (i.e., the open-circuit voltage caused by the light) is la ...
*
Photo-Dember
References
Further reading
*
External links
*
:de:Harry Dember
Electrical phenomena
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