When a collimated beam of monoenergetic
gammaray photons passes through a material, the interaction processes remove
gammarays by
absorption or by scattering the gammarays away from the detector direction. The linear attenuation coefficient :
 describes the probability of absorption occurring per unit length within the absorber
material;
 it is also sometimes related to the density of the absorber material and called the mass attenuation coefficient.
Linear attenuation coefficients for certain gamma energies and absorber materials are
found from linear attenuation graphs.
This
simulation demonstrates how the absorption of gammaray photons varies with the
thickness of absorber material and the type of absorber material. To explore the
relationship between these parameters go to the graph plotting exercise here. The intensity ratio is the ratio of transmitted
intensity to initial intensity (I /I_{0}),
and is expressed as a percentage. 

