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A 100 gram sample of a radioactive element is present at 9 a.m. on Monday and only 25 grams of the element can be detected at 9 a.m. on Friday. What is the half-life of the source?
Wiki User
∙ 15y ago
The half-life is 2 days. You start with 100 grams. In one half life, you will lose 50 grams and have 50 grams remaining. In a second half-life, you will lose 25 of the 50 grams and have 25 grams left. You will have lost 75 grams of a 100 gram sample of radioactive material and have only 25 grams of it left after two half-lives. That means there are two half-lives from 9 a.m. Monday to 9 a.m. Friday. That's 4 days for 2 half-lives, or 2 days for one half-life.
Wiki User
∙ 15y ago
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