Gamma rays are more penetrating than alpha or beta particles because which of the following is true?

• A. They carry charge and interact strongly with matter; require dense shielding.
• B. They are high-energy photons with no charge; require dense shielding such as lead or concrete.
• C. They are slowed by magnetic fields, unlike alpha.
• D. They are charged and deflect easily in air.

Answer: (B)

Gamma rays are uncharged, high-energy photons. Because they have no electric charge, they don’t interact with matter by electric forces the way charged particles do, so they pass through many materials with little attenuation. Their energy is removed mainly through photon-matter interactions—photoelectric effect, Compton scattering, and, at higher energies, pair production—which depend on the material’s density and atomic number. Dense shielding like lead or concrete increases the likelihood of these interactions and thus reduces the gamma-ray beam. That’s why gamma radiation requires thick, dense shielding. The other ideas—gamma rays carrying charge and interacting strongly, being slowed by magnetic fields, or deflected easily in air—don’t fit because gamma rays have no charge, magnetic fields don’t slow them, and they’re not easily deflected in air.