Photoelectric Effect

When photos are taken in darkness, the photograph appears fainter as it breaks up into randomly arranged patches on the film. As the light intensity increases, this will increase the amount of photons which collect in light patches on the film, producing a smoother image. These photons are considered quanta of light.

The picture is built up by events which occur one-by-one with probabilities, not uncertainties. Therefore, a photon may hit a place where the probability is low, in darkness, or not hit when the probability is high. The random arrival of photons, which can be compared to raindrops, is much more obvious when the rate of arrival is low, as someone who is slightly wet must have obviously been walking in light rain.

In 1900, Max Planck, a German physicist, considered that EM radiation is delivered as energy quanta, tiny packets of energy. Einstein extended this in 1905, considering that the discrete packets of energy are also absorbed as quanta.

Planck produced formulae for energy..

h = Js - 6.6*10^-34

For energy emitted by photons or sub-atomic particles, the energy in J is too small to be considered. Therefore, electron volts may be used.

ONE ELECTRON VOLT: Energy transferred by one electron as it travels through a potential difference of one volt.

As work= VQ, 1eV = V*q

-> 1 JC^-1 * (1.6*10^-19)C = 1.6*10^-19 J

The Photo-Electric Effect

This is the emission of electrons when light strikes a surface at a sufficiently high frequency.

Intensity of light is the amount of light transferred per square metre of surface per second. The wave model suggested when light was emitted at a source, the release of photoelectrons would be delayed, and a higher intensity of light would emit photoelectrons…