A) 16 h
B) 6h
C) 10 h
D) 12 h
Correct Answer: D
Solution :
The number of atoms (N) left after n half-lives is \[N={{N}_{0}}{{\left( \frac{1}{2} \right)}^{n}}\] where No is initial number of atoms. Given, \[N=1,\,\,{{N}_{0}}=64\] \[\therefore \] \[\frac{1}{64}={{\left( \frac{1}{2} \right)}^{n}}\] \[\Rightarrow \] \[n=6\] \[\therefore \] Time required \[=n\,{{T}_{1/2}}=6\times 2=12\,h\].
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