If a radioactive isotope that was injected into your bloodstream has a half- life of 5 hours, how many hours do you have to wait before the amount of this isotope in your body is 1 its original 16
Amount?

Question

Quizplus · Accepted Answer

After one half-life, the amount of the radioactive isotope in the body will be 1/2 of the original amount. In this case, the half-life is 5 hours. Therefore, after 5 hours, the amount in the body will be 1/2 of the original.

After another 5 hours (a total of 10 hours since injection), the amount in the body will be 1/4 of the original (1/2 of the amount left after 5 hours).

After another 5 hours (a total of 15 hours since injection), the amount in the body will be 1/8 of the original (1/2 of the amount left after 10 hours).

After another 5 hours (a total of 20 hours since injection), the amount in the body will be 1/16 of the original (1/2 of the amount left after 15 hours).

Therefore, the answer is C (20 hours).

If a Radioactive Isotope That Was Injected into Your Bloodstream