Linear attenuation coefficient

Linear attenuation coefficent (µ) is a constant that describes the the fraction of attenuated incident photons in a monoenergetic beam per unit thickness of a material. Its complement is the transmitted portion of the beam. It is expressed numerically in units of cm-1.

Calculating µ

The intensity of the beam at distance x (cm) within a material is calculated using the following equation 1:


Where Ix is the intensity at depth of x cm, I0 is the original intensity, and µ is the linear attenuation coefficient​.

Rearrange and take the log of both sides gives the equation for µ.

μ = ln(Io/Ix)/x


The mass attenuation coefficient is a normalisation of the linear attenuation coefficient per unit density of a material producing a value that is constant for a given element or compound 2.

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Article information

rID: 31918
Section: Physics
Synonyms or Alternate Spellings:
  • LET

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