ASNT Radiographic Testing Practice Test 2026 – Comprehensive All-in-One Guide for Exam Success!

When radiation from a source such as Co-60 passes through a material like lead, the thickness of the lead plays a crucial role in determining how much radiation is absorbed or attenuated. Lead is a dense material known for its effectiveness as a radiation shield due to its high atomic number, which allows it to significantly impede the passage of gamma radiation.

In this scenario, a piece of lead that is 1/2 inch thick is positioned in the path of the radiation. The behavior of gamma radiation as it interacts with lead follows the principles of exponential attenuation, where the intensity of radiation decreases exponentially with increasing thickness of the absorber.

The specific value for how much the dose rate decreases can vary depending on the energy of the radiation, but for Co-60, which emits gamma rays of significant energy, a thickness of about 1/2 inch would typically reduce the dose rate significantly. The attenuation characteristics suggest that the radiation could be reduced to about one-half, aligning with half-value thickness (HVT) principles.

Therefore, placing a 1/2 inch thick shield of lead in the radiation path is expected to decrease the dose rate to one-half of its original intensity. This represents a critical aspect of radiation safety, as appropriate shielding is essential