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Compton effect vs photolectric effect

  1. Jun 21, 2009 #1
    I understand that according to the photoelectric effect, the photons are apparently 'absorbed' by the electron if it is of the right energy i.e an all or nothing process. But in the Compton effect, the photon scatters off the electron with a change in wavelength? I am trying to get my head over the meaning of that, it does not make much sense. Anyone care to shed some light on it?
  2. jcsd
  3. Jun 21, 2009 #2


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    Well in the photoelectric effect, one needs MORE than the work energy, i.e. not what you say "all or nothing process". You must have confused this with excitation of atoms.

    The photoelectric effect and compton are ionization processes.
  4. Jun 21, 2009 #3
    The photoelectric process (or deep core photoejection process), depends on some charged object (like a nucleus or atomic lattice) to absorb momentum recoil so that both energy and momentum are conserved when the photon strikes the electron.
    When an electron is free (not bound to a nucleus or atomic lattice), a photon cannot transfer all its energy and momentum to the electron. Thus in the Comption process, a secondary photon is created. Normally, the energy of the secondary photon has less energy than the primary photon.

    At the Stanford Linear Accelerator Center (SLAC), experimenters shoot a laser beam (laser photon energy perhaps 2 or 3 eV) at 40 GeV beam of electrons (gamma ~ 80,000). The secondary photon energy from the Compton process is boosted by approximately a factor of 80,0002 to roughly 10 or 12 GeV. This is not an ionizing process.
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