The Photoelectric Effect

The Photoelectric Effect

1. It cannot be explained by wave theory - it supports Planck's theory that light was quantised.

2. 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 photelectrons.

3. 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 zero to some max value. This value of max kinetic energy increases with the frequency of the radiation, and is unaffected by the intensity of the radiation.
     • Conclusion 3: The number of photoelectrons emitted per second is proportional to the intensity of the radiation.

4. According to wave theory:

   • 1. For a particular frequency of light, the energy carried is proportional to the intensity of the beam.
   • 2. The energy carried by the light would be spread evenly over the wavefront.
   • 3. Each free electron on the surface of the metal would gain a bit of energy from each incoming wave.
   • 4. Gradually, each electron would fain enough energy to leave the metal.