The calculation of gamma-ray attenuation by matter is important for:

• assessing the effectiveness of shielding, and
• to correct for self absorption within sources.

Both calculations require the attenuation coefficient (m). 

The attenuation coefficient is the summation of:

• the photoelectric absorption coefficient;
• the Compton scattering coefficient;
• the pair production coefficient, and
• other scattering coefficients.

This section contains the following topics:

Linear attenuation
Build up factor
Attenuation graphs
Questions