Beta particles are best shielded by which of the following?

• A. A dense shielding material like lead
• B. A few millimeters of plastic, glass, or metal foil
• C. Vacuum
• D. Several meters of concrete

Answer: (B)

Beta particles are fast electrons that lose energy quickly as they collide with atoms, so they don’t travel far in matter. A thin layer of material—about a few millimeters—made of plastic, glass, or foil-style metal is enough to stop them for the energies typical in many practical sources. These materials are effective because they provide sufficient stopping power without causing much secondary radiation.

Dense shielding like lead can stop beta, but it has a downside: the decelerating electrons produce bremsstrahlung X-rays in high-Z materials, adding another radiation hazard that requires extra shielding. Vacuum offers nothing to slow or absorb the beta particles, so they would pass through. Several meters of concrete would be excessive for beta and is mainly used for shielding gamma rays, not beta radiation.