“photoelectric effect”的概念、定义、翻译、参考文献-科学参考

photoelectric effect

Physics

The liberation of electrons (see photoelectron) from a substance exposed to electromagnetic radiation. The number of electrons emitted depends on the intensity of the radiation. The kinetic energy of the electrons emitted depends on the frequency of the radiation. The effect is a quantum process in which the radiation is regarded as a stream of photons, each having an energy hf, where h is the Planck constant and f is the frequency of the radiation. A photon can only eject an electron if the photon energy exceeds the work function, ϕ‎, of the solid, i.e. if hf₀=ϕ‎ an electron will be ejected; f₀ is the minimum frequency (or threshold frequency) at which ejection will occur. For many solids the photoelectric effect occurs at ultraviolet frequencies or above, but for some materials (having low work functions) it occurs with light. The maximum kinetic energy, E_m, of the photoelectron is given by Einstein’s equation: E_m=hf − ϕ‎ (see also photoionization). The photoelectric effect has been investigated for many frequencies of electromagnetic radiation, including X-rays and gamma rays.

Apart from the liberation of electrons from atoms, other phenomena are also referred to as photoelectric effects. These are the photoconductive effect and the photovoltaic effect. In the photoconductive effect, an increase in the electrical conductivity of a semiconductor is caused by radiation as a result of the excitation of additional free charge carriers by the incident photons. Photoconductive cells, using such photosensitive materials as cadmium sulphide, are widely used as radiation detectors and light switches (e.g. to switch on street lighting).

In the photovoltaic effect, an e.m.f. is produced between two layers of different materials as a result of irradiation. The effect is made use of in photovoltaic cells, most of which consist of p−n semiconductor junctions (see also photodiode; phototransistor). When photons are absorbed near a p−n junction new free charge carriers are produced (as in photoconductivity); however, in the photovoltaic effect the electric field in the junction region causes the new charge carriers to move, creating a flow of current in an external circuit without the need for a battery. See also photoelectric cell.

Chemistry

The liberation of electrons from a substance exposed to electromagnetic radiation. The number of such electrons (photoelectrons) emitted depends on the intensity of the radiation. The kinetic energy of the electrons emitted depends on the frequency of the radiation. The effect is a quantum process in which the radiation is regarded as a stream of photons, each having an energy hf, where h is the Planck constant and f is the frequency of the radiation. A photon can only eject an electron if the photon energy exceeds the work function, ϕ‎, of the solid, i.e. if hf₀ = ϕ‎ an electron will be ejected; f₀ is the minimum frequency (or threshold frequency) at which ejection will occur. For many solids the photoelectric effect occurs at ultraviolet frequencies or above, but for some materials (having low work functions) it occurs with light. The maximum kinetic energy, E_m, of the photoelectron is given by the Einstein equation: E_m = hf – ϕ‎.
Apart from the liberation of electrons from atoms, other phenomena are also referred to as photoelectric effects. These are the photoconductive effect and the photovoltaic effect. In the photoconductive effect, an increase in the electrical conductivity of a semiconductor is caused by radiation as a result of the excitation of additional free charge carriers by the incident photons. Photoconductive cells, using such photosensitive materials as cadmium sulphide, are widely used as radiation detectors and light switches (e.g. to switch on street lighting).
In the photovoltaic effect, an e.m.f. is produced between two layers of different materials as a result of irradiation. The effect is made use of in photovoltaic cells, most of which consist of p–n semiconductor junctions. When photons are absorbed near a p–n junction new free charge carriers are produced (as in photoconductivity); however, in the photovoltaic effect the electric field in the junction region causes the new charge carriers to move, creating a flow of current in an external circuit without the need for a battery.
The photoelectric effect has been investigated over a very wide range of electromagnetic radiation.

Electronics and Electrical Engineering

An effect, first noticed by Heinrich Hertz, whereby electrons are liberated from matter when it is exposed to electromagnetic radiation of certain energies. In solids electrons are only liberated when the frequency of the exciting radiation is greater than a characteristic value – the photoelectric threshold of the material. The photoelectric threshold is usually in the mid-ultraviolet region of the electromagnetic spectrum for most solids, although some metals exhibit photoelectric emission with visible or near-ultraviolet radiation. It was found that the numbers of electrons ejected from a solid is not dependent on the frequency of the radiation but on the intensity; the maximum velocity however is directly proportional to the frequency.
Einstein explained this phenomenon by assuming that the radiant energy could only be transferred in discrete amounts, i.e. as photons. The energy of each photon is given by hν, where h is the Planck constant and ν the frequency of the incident radiation. Provided that hν exceeds the work function of the material, Φ, an electron in the material absorbing a photon is ejected from the surface. The maximum kinetic energy, E, of the electrons is given by the Einstein photoelectric equation:
$E = h ν - Φ$
Photoelectric emission from a material may be prevented by applying a negative potential to the surface. The minimum potential required to prevent photoelectric emission is the stopping potential.
The photoelectric effect is utilized in some types of photocell and in photomultipliers. See also photoconductivity.

单词	photoelectric effect
释义	photoelectric effect Physics The liberation of electrons (see photoelectron) from a substance exposed to electromagnetic radiation. The number of electrons emitted depends on the intensity of the radiation. The kinetic energy of the electrons emitted depends on the frequency of the radiation. The effect is a quantum process in which the radiation is regarded as a stream of photons, each having an energy hf, where h is the Planck constant and f is the frequency of the radiation. A photon can only eject an electron if the photon energy exceeds the work function, ϕ‎, of the solid, i.e. if hf₀=ϕ‎ an electron will be ejected; f₀ is the minimum frequency (or threshold frequency) at which ejection will occur. For many solids the photoelectric effect occurs at ultraviolet frequencies or above, but for some materials (having low work functions) it occurs with light. The maximum kinetic energy, E_m, of the photoelectron is given by Einstein’s equation: E_m=hf − ϕ‎ (see also photoionization). The photoelectric effect has been investigated for many frequencies of electromagnetic radiation, including X-rays and gamma rays. Apart from the liberation of electrons from atoms, other phenomena are also referred to as photoelectric effects. These are the photoconductive effect and the photovoltaic effect. In the photoconductive effect, an increase in the electrical conductivity of a semiconductor is caused by radiation as a result of the excitation of additional free charge carriers by the incident photons. Photoconductive cells, using such photosensitive materials as cadmium sulphide, are widely used as radiation detectors and light switches (e.g. to switch on street lighting). In the photovoltaic effect, an e.m.f. is produced between two layers of different materials as a result of irradiation. The effect is made use of in photovoltaic cells, most of which consist of p−n semiconductor junctions (see also photodiode; phototransistor). When photons are absorbed near a p−n junction new free charge carriers are produced (as in photoconductivity); however, in the photovoltaic effect the electric field in the junction region causes the new charge carriers to move, creating a flow of current in an external circuit without the need for a battery. See also photoelectric cell. Chemistry The liberation of electrons from a substance exposed to electromagnetic radiation. The number of such electrons (photoelectrons) emitted depends on the intensity of the radiation. The kinetic energy of the electrons emitted depends on the frequency of the radiation. The effect is a quantum process in which the radiation is regarded as a stream of photons, each having an energy hf, where h is the Planck constant and f is the frequency of the radiation. A photon can only eject an electron if the photon energy exceeds the work function, ϕ‎, of the solid, i.e. if hf₀ = ϕ‎ an electron will be ejected; f₀ is the minimum frequency (or threshold frequency) at which ejection will occur. For many solids the photoelectric effect occurs at ultraviolet frequencies or above, but for some materials (having low work functions) it occurs with light. The maximum kinetic energy, E_m, of the photoelectron is given by the Einstein equation: E_m = hf – ϕ‎. Apart from the liberation of electrons from atoms, other phenomena are also referred to as photoelectric effects. These are the photoconductive effect and the photovoltaic effect. In the photoconductive effect, an increase in the electrical conductivity of a semiconductor is caused by radiation as a result of the excitation of additional free charge carriers by the incident photons. Photoconductive cells, using such photosensitive materials as cadmium sulphide, are widely used as radiation detectors and light switches (e.g. to switch on street lighting). In the photovoltaic effect, an e.m.f. is produced between two layers of different materials as a result of irradiation. The effect is made use of in photovoltaic cells, most of which consist of p–n semiconductor junctions. When photons are absorbed near a p–n junction new free charge carriers are produced (as in photoconductivity); however, in the photovoltaic effect the electric field in the junction region causes the new charge carriers to move, creating a flow of current in an external circuit without the need for a battery. The photoelectric effect has been investigated over a very wide range of electromagnetic radiation. Electronics and Electrical Engineering An effect, first noticed by Heinrich Hertz, whereby electrons are liberated from matter when it is exposed to electromagnetic radiation of certain energies. In solids electrons are only liberated when the frequency of the exciting radiation is greater than a characteristic value – the photoelectric threshold of the material. The photoelectric threshold is usually in the mid-ultraviolet region of the electromagnetic spectrum for most solids, although some metals exhibit photoelectric emission with visible or near-ultraviolet radiation. It was found that the numbers of electrons ejected from a solid is not dependent on the frequency of the radiation but on the intensity; the maximum velocity however is directly proportional to the frequency. Einstein explained this phenomenon by assuming that the radiant energy could only be transferred in discrete amounts, i.e. as photons. The energy of each photon is given by hν, where h is the Planck constant and ν the frequency of the incident radiation. Provided that hν exceeds the work function of the material, Φ, an electron in the material absorbing a photon is ejected from the surface. The maximum kinetic energy, E, of the electrons is given by the Einstein photoelectric equation: $E = h ν - Φ$ Photoelectric emission from a material may be prevented by applying a negative potential to the surface. The minimum potential required to prevent photoelectric emission is the stopping potential. The photoelectric effect is utilized in some types of photocell and in photomultipliers. See also photoconductivity.
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