Which shielding material is effective for absorbing gamma radiation?

Which shielding material is effective for absorbing gamma radiation?

• A. Thin plastic.
• B. Lead or metres of concrete.
• C. Wood.
• D. Water vapor.

Answer: (B)

Gamma radiation consists of high-energy photons that can pass through many materials, so shielding relies on absorbing or scattering those photons. The material’s density and atomic number determine how effectively it attenuates gamma rays—higher density and higher atomic number increase interaction probabilities and reduce the beam more quickly. Lead is superb for this purpose because it’s very dense and has a high atomic number, which boosts the chances of photoelectric absorption and other interactions that remove energy from the gamma ray. Concrete also provides good shielding, but you need a much thicker layer—often several inches to feet—because it’s less dense and has a lower effective atomic number than lead. In contrast, thin plastics or woods are light and low in density, offering only small attenuation per thickness, and water vapor, being a gas, provides very little shielding unless you surround the source with an impractically large volume. So the most effective shielding materials for gamma radiation are dense, high-Z substances like lead, or a sufficiently thick layer of concrete.

Gamma radiation consists of high-energy photons that can pass through many materials, so shielding relies on absorbing or scattering those photons. The material’s density and atomic number determine how effectively it attenuates gamma rays—higher density and higher atomic number increase interaction probabilities and reduce the beam more quickly.

Lead is superb for this purpose because it’s very dense and has a high atomic number, which boosts the chances of photoelectric absorption and other interactions that remove energy from the gamma ray. Concrete also provides good shielding, but you need a much thicker layer—often several inches to feet—because it’s less dense and has a lower effective atomic number than lead.

In contrast, thin plastics or woods are light and low in density, offering only small attenuation per thickness, and water vapor, being a gas, provides very little shielding unless you surround the source with an impractically large volume. So the most effective shielding materials for gamma radiation are dense, high-Z substances like lead, or a sufficiently thick layer of concrete.