1.

Half-life for radioactive C^(14) is 5760 years. In how many years 200 mg of C^(14) sample will be reduced to 25 mg

Answer»

11520 years
23040 years
5760 years
17280 years

Solution :`25 = [(1)/(2)]^(N) xx 200, [(1)/(2)]^(n) = (25)/(200) = (1)/(8) = [(1)/(2)]^(3)`
n = 3, NUMBER of half lives = 3
so time required `= 3xx 5760 = 17280 yr`


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