ASNT Industrial Radiography Radiation Safety Test 2026 – 400 Free Practice Questions to Pass the Exam

To determine how much exposure is reduced by 0.57 inches of lead when 0.19 inches provides 1 half-value layer (HVL), it is essential to first understand the concept of half-value layers in radiation shielding.

A half-value layer is the thickness of material required to reduce the intensity of radiation by half. Therefore, if 0.19 inches of lead reduces the radiation exposure by 50%, then applying additional HVLs will continue to reduce the exposure exponentially.

Calculating the number of half-value layers in 0.57 inches requires finding how many times 0.19 inches fits into 0.57 inches. Dividing 0.57 by 0.19 gives approximately 3.0, implying that 0.57 inches of lead represents about three half-value layers.

Each half-value layer reduces the exposure to half of its previous amount:

- After the first HVL (0.19 in), the exposure is reduced to 50% of the original.

- After the second HVL (0.38 in total), the exposure is reduced to 25% of the original.

- After the third HVL (0.57 in total), the exposure is reduced to 12.5% of