Which radiation can penetrate through thick materials and is the most difficult to shield against?

Gamma radiation is the most penetrating type of radiation listed, capable of traveling through thick materials such as concrete and lead. This is due to its high energy and lack of mass, which allows gamma rays to pass through materials without being easily absorbed or scattered. Unlike alpha and beta radiation, which can be blocked by relatively thin barriers, gamma rays require denser materials for effective shielding.

For instance, while alpha particles can be stopped by a sheet of paper and beta particles can be mitigated by plastic or glass, gamma rays require much thicker layers of shielding—often several centimeters of lead or significant thicknesses of concrete—to reduce their intensity significantly. This characteristic makes them particularly challenging in radiation safety practices, as effective shielding can be cumbersome and costly.

X-rays, while also penetrating, have slightly different properties and energy levels compared to gamma radiation, making them less challenging to shield against in many situations, particularly in medical settings.