Changes

==Modern Theory==

==Modern Theory==

The modern theory of the photoelectric effect is based in the quantum theory proposed by [[Planck]]. Planck postulated that light was not a continuous wave but a series of discrete packets or quanta of energy distributed over a wavefront. Planck's theory was confirmed by some experiments by von Lenard in 1902. The phenomenon was thus explained as such:

 

The modern theory of the photoelectric effect is based in the quantum theory proposed by [[Planck]]. In 1905 Einstein applied this to the photoelectric effect, postulating that light was not a continuous wave but a series of discrete packets or quanta of energy distributed over a wavefront. This "discovery of the law of the photoelectric effect" (explaining the effect in terms of quantized energy and providing equations) was the reason the Nobel Prize Committee awarded Einstein the Nobel Prize in 1921.<ref>[http://www.relativitycalculator.com/photoelectric_effect.shtml]</ref> 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''