Figure 2.

Mechanisms of attenuation of an electromagnetic radiation of energy $E_i$, incident on a shielding layer of thickness t: reflection, multiple reflections, and absorption. $E_r$($E_t$) is the reflected (transmitted) energy, and $E_r$’($E_t$’) is the energy reflected (transmitted) after multiple crossing the layer. Color attenuation represents attenuation of energy.