A thickness of 0.19 inches of lead is known to reduce the exposure of Ir-192 by what factor?

The correct answer, indicating that a thickness of 0.19 inches of lead reduces the exposure of Ir-192 by a factor of one-half, relates to the concept of half-value layer (HVL). The HVL is the thickness of material needed to reduce the intensity of radiation to half its original value.

In the case of Ir-192, which emits gamma radiation, lead is a common shielding material due to its high density and effective attenuation properties. The specific thickness of lead that corresponds to the HVL for Ir-192 is approximately 0.19 inches. When this thickness is applied for shielding, it effectively decreases the radiation exposure to 50% of what it would be without this shielding. This principle is crucial for radiation safety practices, as it allows professionals to determine how much shielding is necessary to ensure safe working conditions around radioactive materials.

Understanding this relationship between lead thickness and exposure reduction is fundamental in radiation safety, allowing individuals to limit their exposure and protect themselves effectively while working with or near radioactive sources.