What type of radiation generally requires a lead shield for effective protection?

Gamma radiation requires a lead shield for effective protection due to its highly penetrating nature. Gamma rays are electromagnetic radiation with high energy that can travel significant distances and pass through most materials, including human tissue. In order to effectively reduce their intensity and safeguard against exposure, dense materials such as lead are utilized, since lead has a high atomic number and is particularly effective in attenuating gamma radiation.

While other types of radiation, such as alpha and beta radiation, have different shielding requirements—alpha particles can typically be stopped by a sheet of paper or even human skin, and beta particles require less dense materials, such as plastic or glass—gamma radiation's penetration capability makes lead the preferred choice for effective shielding. X-rays, while also penetrating, generally require less dense materials than lead for shielding, depending on the energy of the x-rays in question. Therefore, the unique characteristics of gamma radiation define the necessity for lead shielding.