What material is effective in stopping gamma rays?

Gamma rays are highly penetrating electromagnetic radiation, and materials that effectively attenuate gamma rays typically have high atomic numbers and density. Lead is one of the most effective materials for shielding against gamma radiation due to its high density, which allows it to absorb and scatter the gamma photons effectively.

When several inches of lead are used, the interaction with the gamma rays occurs through processes such as photoelectric absorption and Compton scattering, which are essential for reducing the intensity of the gamma radiation passing through the material. The thicker the layer of lead, the more effective it is at attenuating the radiation.

In contrast, lighter materials or those with low atomic numbers, such as aluminum, paper, or drywall, are significantly less effective at stopping gamma rays. They simply do not possess the necessary density or atomic structure to absorb gamma radiation effectively. Therefore, using several inches of lead is the most effective method for providing adequate shielding against gamma rays.