ASNT Industrial Radiography Radiation Safety Practice Test

How many half-lives does Ir-192 undergo after 148 days?

1. 1 half-life

2. 2 half-lives

3. 3 half-lives

4. 4 half-lives

The correct answer is: 2 half-lives

To determine how many half-lives Iridium-192 (Ir-192) undergoes after 148 days, it is essential to know the half-life of Ir-192, which is approximately 73.8 days. To find the number of half-lives that pass in a total period of 148 days, you can divide the total time (148 days) by the half-life duration (73.8 days): 148 days ÷ 73.8 days/half-life ≈ 2.0 half-lives. Since this calculation results in approximately 2.0, it reveals that Ir-192 undergoes a little over 2 half-lives in that time frame, but it does not complete the third half-life. Thus, stating that 2 half-lives have occurred is accurate. This understanding illustrates the decay process of radioisotopes and is crucial in radiography settings to anticipate the radiation levels and ensure safety protocols are appropriately followed.