BRAINCAKEX-ray Attenuation Mechanisms
When a beam of X-rays passes through matter, its intensity falls. This is called attenuation. Photons are removed from the beam either by being absorbed or by being scattered out of it.
The OCR specification lists four attenuation mechanisms. Which one happens depends mainly on the photon energy:
• Simple scatter: 1 to 20 keV
• Photoelectric effect: below about 100 keV
• Compton effect: about 0.5 to 5 MeV
• Pair production: above 1.02 MeV
Sign in free to see the rest of this lesson, the R.E.C.I.P.E. recall steps and the quiz
BrainCake is free. Make an account in seconds and pick up where this page stops.
Key terms in this lesson
- photoelectric effect
- The complete absorption of a photon by an inner electron of an atom, which is ejected, transferring the photon's energy to the electron.
- compton effect
- The scattering of a photon by an outer electron, in which the electron is ejected and the photon loses energy and changes direction.
- pair production
- The process in which a high-energy photon near a nucleus is converted into a particle-antiparticle pair, such as an electron and a positron.
More in Medical Imaging
- Production of X-rays
- X-ray Tubes
- Photoelectric Effect, Compton Scattering and Pair Production
- Attenuation of X-rays
- Contrast Media
- CAT Scanning
- Medical Tracers
- Technetium-99m and Fluorine-18
All 20 lessons in Medical Imaging · All OCR A-level Physics topics