In gamma shielding, attenuation with thickness is described by which relation?

• A. Attenuation is linear with thickness
• B. Attenuation is exponential with thickness; depends on density and material
• C. Attenuation is independent of energy
• D. Attenuation increases with photon energy only

Answer: (B)

Attenuation of gamma rays through shielding is exponential with thickness, governed by the linear attenuation coefficient μ. The transmitted intensity is I = I0 exp(-μ x). Here μ depends on the material (through its density and composition) and on the photon energy. A denser, high‑Z material increases μ and thus strengthens shielding, while higher photon energy generally reduces μ, making attenuation less for the same thickness. So the best description is an exponential decrease with thickness that depends on material properties and energy. The other statements are not correct: attenuation is not linear with thickness, it does depend on energy, and it does not simply increase with photon energy.