Photoelectric Effect

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Photoelectric Effect
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Predictions of the Wave Theory
- the light intensity should influence the
maximum KE of electrons - the frequency of the
light should not affect the KE of ejected
electrons.
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Photon Theory
Light is a particle again Ehf
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• The energy of photon is the same for all photons
  in a monochromatic beam.
• Increasing of the intensity of the light means
  increasing of the number of photons in the beam,
  but does not affect the energy of each photon as
  long as the frequency is not changed.

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According to Einstein, electron is ejected from
the metal by a collision with a single photon.
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• An increase in intensity of the light beam means
  more photons are incident, so more electrons will
  be ejected , but max KE in not changed.
• If the frequency of the light is increased, the
  max KE increases linearly.
• If the frequency f is less than the cutoff
  frequency f0, no electrons will be ejected at
  all, no matter how big is the intensity.

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Compton Effect
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Photon Interaction

• A photon can be scattered (Compton effect).
• A photon may knock an electron out of an atom
  (Photoelectric effect).
• A photon may knock an electron to a higher energy
  state in the atom (excited state of the atom).
• A photon can actually create matter (pair
  production).

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Pair Production
What is (a) the minimum of a photon, that can
produce an electron-positron pair? (b) What is
this photons wavelength?
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Wave-Particle Duality
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Wave Nature of Matter
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De Broglie Wavelength