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After a certain lapse of time , fraction...

After a certain lapse of time , fraction of radioactive polonium undecayed is found to be 12.5 % of the initial quantity. What is the duration of this time lapse, if half-life of polonium is 139 days?

Text Solution

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The correct Answer is:
417 days
`N/N_0=(1/2)^n rArr 125/1000 = (1/2)^n rArr n=3, t=nT_(1//2)`
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