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The modern theory of the photoelectric effect is based in the quantum theory proposed by [[Max Planck|Planck]].

The modern theory of the photoelectric effect is based in the quantum theory proposed by [[Max Planck|Planck]].

In 1900, he published the idea that the energy emitted by a resonator could only take on discrete values or quanta. The energy for a resonator of frequency v is hv where h is a universal constant, now called Planck's constant.<ref>[http://nobelprize.org/nobel_prizes/physics/laureates/1918/planck-bio.html]</ref> In 1902, Lenard showed that the energy of electrons in the photoelectric effect depended only on the frequency of the incident light. In 1905, Einstein showed that Planck's formula could be used to give a heuristic explanation of Lenard's results. The phenomenon was thus explained as such:

In 1900, he published the idea that the energy emitted by a resonator could only take on discrete values or quanta. The energy for a resonator of frequency v is hv where h is a universal constant, now called Planck's constant.<ref>[http://nobelprize.org/nobel_prizes/physics/laureates/1918/planck-bio.html]</ref> In 1902, Lenard showed that the energy of electrons in the photoelectric effect depended only on the frequency of the incident light. In 1905, Einstein showed that Planck's formula could be used to give a heuristic explanation of Lenard's results. The phenomenon was thus explained as such:

* Each photon contained energy based solely on frequency, such that E = hf where h is Planck's constant (6.626 x 10^-34)

* Each photon contained energy based solely on frequency, such that E = hf where h is Planck's constant (6.626 x 10⁻³⁴)

* Electrons could be emitted if they received sufficient energy from a photon. However, this was an "all or nothing" transfer and emission would only occur if the single photon contained enough energy to overcome the ''work function'' of the material. The minimum frequency to cause emission is known as the ''threshold frequency''

* Electrons could be emitted if they received sufficient energy from a photon. However, this was an "all or nothing" transfer and emission would only occur if the single photon contained enough energy to overcome the ''work function'' of the material. The minimum frequency to cause emission is known as the ''threshold frequency''

* The kinetic energy of each photon is the difference between the energy carried by the photon and the work function of the material

* The kinetic energy of each photon is the difference between the energy carried by the photon and the work function of the material

Lenard, Planck, and Einstein won the [[Nobel Prize]] in physics in 1905, 1918 and 1921 respectively.  Lenard was cited "for his work on cathode rays," Planck was cited "in recognition of the services he rendered to the advancement of Physics by his discovery of energy quanta" and Einstein's was cited for his "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect."<ref>[http://nobelprize.org/nobel_prizes/physics/laureates/1905/]</ref><ref>[http://nobelprize.org/nobel_prizes/physics/laureates/1918/index.html]</ref><ref>[http://nobelprize.org/nobel_prizes/physics/laureates/1921/]</ref>

Lenard, Planck, and Einstein won the [[Nobel Prize]] in physics in 1905, 1918 and 1921 respectively.  Lenard was cited "for his work on cathode rays," Planck was cited "in recognition of the services he rendered to the advancement of Physics by his discovery of energy quanta" and Einstein's was cited for his "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect."<ref>[http://nobelprize.org/nobel_prizes/physics/laureates/1905/]</ref><ref>[http://nobelprize.org/nobel_prizes/physics/laureates/1918/index.html]</ref><ref>[http://nobelprize.org/nobel_prizes/physics/laureates/1921/]</ref>

==See Also==

==See also==

* [[Quantum mechanics]]

* [[Quantum mechanics]]

[[Category:Physics]]

[[Category:Physics]]

==External Links==

==External links==

*[http://www.relativitycalculator.com/photoelectric_effect.shtml The Photoelectric Effect ]

*[http://www.relativitycalculator.com/photoelectric_effect.shtml The Photoelectric Effect ]

==References==

==References==