Photoelectric+Effect

=Photoelectric Effect=

Theory
Even in the early 1900’s it was well known that a metal placed under an ultraviolet light would emit electrons. However, the surprising experimental discovery was that light with low frequencies, no matter of intensity, would not knock the electrons in the metal loose.

To resolve this problem, Einstein discarded the well established wave model of light for a particle model. Building on Plank’s blackbody work, he theorized that light comes in packets called photons that each have a very specific amount of energy which depends on the frequency of light. Einstein thought about intensity in terms of the number of photons emitted.

Like the Bohr model of the atom, Einstein thought that a photon with a specific amount of energy, equal to the difference in electron energy levels, must be absorbed by the metal to release the electron. He thought that each electron emission was the result of a single photon collision and absorption. Thus he reasoned that an infinite number of low energy photons could not release any electrons since each individual photon did not have sufficient energy to release any electron.

Although Einstein’s particle model explained the photoelectric effect nicely, it conflicted with previously observed wave properties of light. It took quantum mechanics to resolve this apparent conflict.

Links
Breif history of the photoelectric effect: []

A photoelectric effect experiment: []