Attenuation Coefficients

X-Ray Radiography | | Attenuation

For X-rays the attenuation is proportional

  • to the electro density of the material
    • (approximately linear proportional)
  • to length of the travelled distance
    • (inverse exponentially proportional)

Attenuation per distance is expressed via attenuation coefficient $\mu$

  • Electron density $\approx$ atomic number (in the periodic system of elements)
  • $\mu$ is linear proportional to the atomic number

For water the attenuation coefficient is about $0.15cm^{-1}$.


  • Lead $Pb$ → atomic number 82
  • Water $H_2O$ → atomic number ca. 8+1+1
  • Thus, lead has a 10 times higher attenuation than water.

X-Ray Radiography | | Attenuation