QUANTUM BEHAVIOUR

QUANTUM BEHAVIOUR

1. The Photoelectric Effect

   • The photoelectric effect is when a light with a high enough frequency is shone onto the surface of a metal and causes electrons to be emitted.
     • For most metals, this frequency falls in the U.V. range.
     • 1. Free electrons on the surface of the metal absorb energy from the light making them vibrate. 2. If an electron absorbs enough energy, the bonds holding it to the metal break and the electron is released. 3. This is called the photoelectric effect and the electrons emitted are called photoelectrons.
   • One of the first experiments with light which couldn't be explained with wave theory - It supported Planck's theory that light was quantised.
   • CONCLUSION 1: For a given metal, no photoelectrons are emitted if the radiation has a frequency below a certain value - called the threshold frequency.
   • CONCLUSION 2: The photoelectrons are emitted with a variety of kinetic energies ranging from 0 - some max value. This value of max kinetic energy increases with the frequency of the radiation, and it unaffected by the intensity of the radiation.
   • CONCLUSION 3: The number of photoelectrons emitted per second is proportional to the intensity of the radiation.
   • The photoelectric effect couldn't be explained by wave theory.
     • According to wave theory: