Which radiation type requires shielding with lead, steel, or concrete due to its high penetrating power?

• A. Beta
• B. Neutron
• C. Gamma
• D. Electron

Answer: (C)

Gamma radiation is a highly penetrating form of electromagnetic radiation. Because these photons have no charge and can pass through most materials, shielding needs to be dense and thick. Dense, high‑Z materials like lead, steel, or concrete increase the likelihood that gamma photons interact and lose energy through processes such as the photoelectric effect, Compton scattering, or pair production, reducing the radiation that gets through. The required shielding thickness grows with the gamma energy, often described in half-value layers for a given material.

In contrast, beta and electrons are charged particles with limited range and are stopped by relatively thin layers of material, while neutrons are neutral and require hydrogen-rich moderators and absorbers.