Attenuation coefficient
The quantity attenuation coefficient (commonly denoted by the Greek letter μ) describes how easily electromagnetic radiationthe penetrates into matter. Instead of the linear attenuation coefficient μ (in m-1), often the mass attenuation coefficient μ/ρ (in m2·kg-1) is given. Here, ρ is the density (in kg·m-3) of the material.The quantity half-value thickness (d½) is the amount of material that reduces the intensity to half the original value. The relation between half-value thickness and attenuation coefficient is:
d½ = ln(2) / μ