What type of material is effective as shielding against gamma radiation?

Dense materials like lead or thick concrete are particularly effective as shielding against gamma radiation due to their high atomic number and density. Gamma rays are highly penetrative electromagnetic radiation that possesses significant energy, enabling them to pass through many materials with ease. Dense materials have the capability to absorb or scatter these high-energy photons, significantly reducing the intensity of radiation that can penetrate through them.

Lead, for example, has a high density and a high atomic number, which enhances its ability to shield against gamma radiation effectively. Similarly, thick concrete, which is also a dense material, can provide substantial protection, especially when its thickness is sufficient to attenuate the radiation adequately. This principle of using dense materials for effective shielding is based on the interactions between the gamma rays and the electrons in the shielding material, which leads to a decrease in radiation exposure levels in areas behind the shield.