Half-value thickness

The quantity half-value thickness (d_½) is the amount of material that reduces the radiation intensity to half the original value. Instead of the linear half-value thickness d_½ (in m), often the mass half-value thickness ρd_½ (in kg/m²) is given. Here, ρ is the density (in kg/m³) of the material.

The quantity attenuation coefficient (commonly denoted by the Greek letter μ) describes how easily electromagnetic radiation penetrates into matter. The relation between half-value thickness and attenuation coefficient is:

μ = ln(2) / d_½

Related quantities

• attenuation coefficient
• buildup factor
• dose conversion coefficient
• kerma-rate constant
• radiotoxicity equivalent
• square law
• transmission