InterviewSolution
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InterviewSolution
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There is a stream of neutrons with KE=2eV. If the half life of neutrons is 100 sec, what fraction of neutrons will decay before they travel a distance of 1000 km. [Mass of neutrons `=1.6 xx10^(-24)g`]A. `0.75`B. `0.25`C. `0.707`D. `0.293` |
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Answer» Correct Answer - D `(1)/(2)MV^(2) rArr 2 eV` `V=sqrt((4eV)/(m))` `V=sqrt((4eV)/(1.6 xx 10^(-27))) " " l eV=1.6 xx 10^(-19)J` `sqrt((4 xx1.6 xx 10^(-19 )J)/(1.6 xx 10^(-27))) rArr V= sqrt(4 xx 10^(8))=2 xx 10^(4)m//s` `t=(1000 xx 1000m)/(V) rArr t= (10^(6)m)/(2 xx 10^(4))= 50 sec` `t=(t_(1//2))/(ln2) ln .(1)/((1-x)) rArr 50 = (100)/(ln2)ln .(1)/(1-x) rArr x=0.293` |
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