An Etymological Dictionary of Astronomy and Astrophysics
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The falling off of the energy density of radiation with distance from the source, or with passage through an absorbing or scattering medium.

Verbal noun of → attenuate.

The fraction of a beam of → X-rays or → gamma rays that is absorbed or scattered per unit thickness of the → absorber. The linear attenuation coefficient, denoted by the symbol μ, appears in the equation I(x) = I₀e^-μx, where I(x) is the intensity at depth of x cm and I₀ is the original intensity.

→ attenuation; → coefficient.

The ratio of the radiation intensity after traversing a layer of matter to its intensity before.

→ attenuation; → factor.