Explain the photo-electric effect and how the particle theory of light explains the phenomena. State the equation used to the determine the kinetic energy of a photo-electron and explain the origin of the terms used in your equation.

The photoelectric effect is the stimulated emission of electrons due to the irradiation of photons onto the surface of a metal. The increase in the frequency of the photons doesn’t lead to an increase in the number of photo-electrons, but the kinetic energy of the individual photoelectrons. This can be explained if light was comprised of individual particles with a quantised amount of energy. One of these quantised light particles, or photons, can only ionise one electron and any “left over” energy from ionisation is in the form of the kinetic energy of the electron. Ekin = hf - wfThe Kinetic energy is the difference between the energy of the incoming photon and the energy needed to liberate one of the surface electrons. This is called the work function.