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A radioactive element gets spilled over the floor of a room. Its half-life period is 30 days. If the initial velocity is ten times the permissible value, after how many days will it be safe to enter the room?
- 100 days
- 1000 days
- 300 days
- 10 days
Correct answer: 100 days
Solution
Activity must fall to 1/10 of its current value. (1/2)^(t/T) = 1/10 with T = 30 days gives t = 30 * log10/log2 = 30 * 3.32 ~ 99.7 = 100 days. Correct answer: 100 days.
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