The Photoelectric Effect


If you shine light of a high enough frequency onto te suface of a metal, it will emit electrons; for most metals, this frequency falls in the ultra violet range.

  • Delocalised electrons on the suface of the metal absorb energy from the light (E=hf) making them vibrate.
  • If an electron absorbs enough energy, the bonds holding it to the metal break and the electron is liberated.
  • This is called the photoelectric effect, and the electrons emitted are called photoelectrons.

The three main conclusions of this experiment are:

  • For a given metal, no photoelectrons are emittedd if the radiation had a frequency below a certain value - the threshold frequency.
  • The photoelectrons are emitted with a variety of different kinetic energies reanging from zero to some maximum value. The maximum value increase with thr frequency of radiation and is unaffected by the inensity of the radiation.
  • The number of photoelectrons emitted per second is proportional to the intensity of the radiation.

The photoelectric effect cannot be explained by wave theory.

According to wave theory:

  • For a particular frequency of light, tehe energy carried is proportional tot the intensity of the beam.
  • The energy carried by the light would


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