Which materials illustrate shielding?

• A. Lead blankets, walls, paper, plastic, water
• B. Glass, metal
• C. Air
• D. Vacuum

Answer: (A)

Shielding means reducing radiation exposure by absorbing or scattering the energy as it passes through material. The best shielding materials are those that interact readily with the type of radiation in question. Lead and thick walls are classic shielding for gamma rays because lead’s high density and atomic number make it very effective at absorbing photons across the common gamma energies. Paper and plastic, while not suitable for shielding high-energy gamma rays, can stop or reduce alpha particles and provide some protection against beta radiation, with the amount needed depending on the particle energy. Water is also a strong shielding material because it is dense and rich in hydrogen, which is effective for slowing neutrons and can help attenuate gamma radiation as well.

Air and vacuum don’t provide meaningful shielding for most radiation types, since there’s little material to absorb or scatter the energy. Glass and metal can offer some attenuation, but they’re not as broadly effective as the combination of dense, high-Z materials (like lead), concrete, or hydrogen-rich substances (like water) for a range of radiation types.