Final answer:
The lead equivalency required for a protective curtain should ensure high absorption of gamma rays, but the given options a. 0.25 mm b. 0.5 mm c. 1 mm d. 2 mm do not provide enough context to decide. More information on operational standards or the specific radiation levels would be needed.
Step-by-step explanation:
To determine the lead equivalency required for an image intensifier's protective curtain, we look closely at how lead absorbs radiation. The question provided two scenarios for reference. In one, 0.170-mm-thick lead shielding absorbs half of the gamma rays from 99mTc. In another, a 1.50-cm-thick lead can absorb 90.0% of the gamma rays, and we need to find out how thick the lead should be to absorb all but 0.100% of the gamma rays.
For the protective curtain, we need a lead equivalency that ensures a high level of absorption of gamma rays for safety. The equivalency should reflect the shielding capability of the lead to absorb gamma rays efficiently and protect against radiation exposure.