12.2.3

Photoelectricity

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Einstein's Photon Model

Albert Einstein came up with the photon model of light to overcome the ultraviolet catastrophe.

Illustrative background for Black bodiesIllustrative background for Black bodies ?? "content

Black bodies

  • A black body is an object which absorbs and emits 100% of the radiation incident upon it.
  • Black bodies have a very specific emission spectrum.
Illustrative background for The ultraviolet catastropheIllustrative background for The ultraviolet catastrophe ?? "content

The ultraviolet catastrophe

  • Wave theory could not explain all of the intensity - wavelength graph for black bodies.
    • This was known as the ultraviolet catastrophe.
  • Wave theory predicted that the power output would continue to rise as the wavelength approached zero.
  • The observation was that the power output curved back towards zero.
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Einstein's photon model of light

  • Max Planck suggested that electromagnetic waves might only be released in quanta.
  • Einstein further suggested that electromagnetic waves can only exist in quanta, called photons.
  • The photon model was able to explain the photoelectric effect, and the ultraviolet catastrophe.

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1Measurements & Errors

2Particles & Radiation

3Waves

4Mechanics & Materials

5Electricity

6Further Mechanics & Thermal Physics (A2 only)

7Fields & Their Consequences (A2 only)

8Nuclear Physics (A2 only)

9Option: Astrophysics (A2 only)

10Option: Medical Physics (A2 only)

11Option: Engineering Physics (A2 only)

12Option: Turning Points in Physics (A2 only)

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