A60-g sample of radioactive isotope is measured after two half-lives have passed. what pair of percentages describes the sample after two half-lives? 50% unchanged and 50% stable 25% unchanged and 75% stable 12.5% unchanged and 87.5% stable 75% unchanged and 25% stable

25% unchanged and 75% stable

Explanation:

The half-life of a radioactive sample is the time it takes for half of the sample to decay and become stable.

In this situation, we have:

- Initial sample: 60 g

- After 1 half-life: half of the sample decays --> 30 g decays and becomes stable, while 30 g of the sample are unchanged

- After 2 half-life: half of the unchanged sample (30 g) decays --> so, 15 g decays and becomes stable, so the new stable sample is 15 g + 30 g = 45 g, while the unchanged sample is 15 g

So, after 2 half-lives we have:

- Unchanged sample:

- Stable sample:

So correct answer is

25% unchanged and 75% stable

the amount of current in the coil

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