604
edits
Changes
[[..]]
==Observations==
==Observations==
The photoelectric effect was first observed by [[Hertz]] when he was investigating the transmission of radio waves. He found that shining [[UV|ultraviolet light]] onto the receiver increased the intensity of the spark produced. This was further investigated by von Lenard, who made a series of observations, some of which could not be explained by the classical wave theory of light:
The photoelectric effect was first observed by [[Heinrich Hertz|Hertz]] when he was investigating the transmission of radio waves. He found that shining [[UV|ultraviolet light]] onto the receiver increased the intensity of the spark produced. This was further investigated by [[Philipp Lenard|von Lenard]], who made a series of observations, some of which could not be explained by the classical wave theory of light:
* Electrons were only emitted above a certain frequency and that this emission was spontaneous, classical theory stated that they would absorb the energy until they could leave the atom
* Electrons were only emitted above a certain frequency and that this emission was spontaneous, classical theory stated that they would absorb the energy until they could leave the atom
* The kinetic energy of the electrons (found by applying a stopping voltage) was dependent only on frequency, classical theory stated that this would be also affected by intensity
* The kinetic energy of the electrons (found by applying a stopping voltage) was dependent only on frequency, classical theory stated that this would be also affected by intensity
==Modern Theory==
==Modern Theory==
The modern theory of the photoelectric effect is based in the quantum theory proposed by [[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<sup>-34</sup>)
* Each photon contained energy based solely on frequency, such that E = hf where h is Planck's constant (6.626 x 10<sup>-34</sup>)