Compton effect

Compton effect or Compton scatter is one of three principle forms of photon interaction. It is the main cause of scattered radiation in a material. It occurs due to the interaction of the x-ray or gamma photon with free electrons (unattached to atoms) or loosely bound valence shell (outer shell) electrons. The resultant incident photon gets scattered (changes direction) and imparts energy to the electron (recoil electron). The scattered photon will have a different wavelength (observed phenomenon) and thus a different energy (E=hc/λ). Energy and momentum are conserved in this process. The Compton effect is a partial absorption process and as the original photon has lost energy, this is known as Compton shift (the shift being a shift of wavelength/frequency).

Probability of Compton effect 
  • directly proportional to
    • number of outer shell electrons, i.e. the electron density
    • physical density of the material
  • inversely proportional to
    • photon energy
  • does not depend on

In other words, the probability of a Compton effect is dependent on the number of electrons in the absorbing material which for almost all elements is approximately the same per unit mass. Thus, the Compton effect is independent of the atomic number (Z) of the absorber.

History and etymology

Named after Professor Arthur Holly Compton (1892-1962), US physicist, who was awarded the Nobel Prize in Physics in 1927 for his discovery of Compton effect 2


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Article Information

rID: 30308
Section: Physics
Tags: physics, refs
Synonyms or Alternate Spellings:
  • Compton
  • Compton scatter

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