NEET Physics Nuclei Questions Solved

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NEET - 2010

The activity of a radioactive sample is measured as N0 counts per minute at t=0 and N0/e counts per minute at t=5 min.The time (in minute) at which the activity reduces to half its value is 

(a) loge2/5                                                         (b) 5loge 2

(c) 5 log10 2                                                         (d) 5 loge 2

Fraction remains after n half lives 


Given       N=N0eN0eN0=125/T

or           1e=125/T

Taking log on both sides, we get 

log 1-log e =5Tlog12

-1=5T-log 2

           T=5loge 2

Now, let t' be the time after which activity reduces to half 




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