A shielding device constructed with a thickness equivalent to 2 half-value layers (HVL) will reduce the quantity of radiation to:

A shielding device constructed with a thickness equivalent to 2 half-value layers (HVL) will reduce the quantity of radiation to:

• A. 75% of the original quantity
• B. 50% of the original quantity
• C. 25% of the original quantity
• D. 12.5% of the original quantity

Answer: (C)

Attenuation by shielding is described by half-value layers: the thickness that reduces the radiation by half. If you have shielding equal to two HVLs, the beam is halved twice, so the remaining quantity is (1/2) × (1/2) = 1/4 of the original, which is 25%. So the radiation is reduced to a quarter of its original amount. For context, one HVL leaves 50% of the original, and three HVLs would leave 12.5%.

Attenuation by shielding is described by half-value layers: the thickness that reduces the radiation by half. If you have shielding equal to two HVLs, the beam is halved twice, so the remaining quantity is (1/2) × (1/2) = 1/4 of the original, which is 25%. So the radiation is reduced to a quarter of its original amount. For context, one HVL leaves 50% of the original, and three HVLs would leave 12.5%.