TOC 1 Physics 222 Photoelectric Effect Light (and all electromagnetic phenomena) is made up of photons. The speed (energy) of the electrons is determined by the frequency of the light. Conservation of energy tells us that the energy of the light must be determined by its frequency. The number of the electrons is determined by the intensity of the light. This tells us that the intensity of light must be related to a number of particles which we call photons.

TOC 2 Physics 222 Photoelectric Effect Light (and all electromagnetic phenomena) is made up of photon-waves. Note that the interference pattern is starting to form! TOC 2

3 Physics 222 Photoelectric Effect These are the energy levels for a HeNe Laser.

TOC 4 Physics 222 Photoelectric Effect The electrons move from one level to another. 2. Energy enters the laser by electric discharge current flow when the electrons collide with the Helium atoms. 1. All atoms start in the ground state. 3. HE atoms collide with NE atoms and move energy from F2 to E4 and F3 to E6. 4. Spontaneous emission occurs from E6 to E3. 5. Stimulated emission occurs when another photon passes through the atom.