What would the radiation reading be after 2 half-lives if a radiographer has 60 mR at the surface of the exposure device?

After two half-lives, the radiation reading can be calculated by understanding how the concept of half-life affects the amount of radiation remaining. The half-life of a radioactive material is the time it takes for half of the material to decay.

Starting with an initial radiation reading of 60 mR (milliroentgens), the first half-life would reduce this amount by half. So, after the first half-life, the reading would drop to 30 mR.

After the second half-life, the same reduction occurs again. Taking the 30 mR remaining from the first half-life, halving it results in a final reading of 15 mR.

This iterative process of halving the radiation is fundamental in understanding radioactive decay and its implications in radiation safety. The answer of 15 mR after two half-lives accurately reflects the continuous decrease in the radiation levels as time progresses, demonstrating the effectiveness of the half-life concept in measuring radiation exposure.