CMC Medical CMC-Medical VELLORE Solved Paper-2007

  • question_answer
    The half-value period of a radioactive nucleide is 3 h. In 9 h its activity will be reduced by a factor of

    A)  \[\frac{1}{9}\]                                  

    B)  \[\frac{1}{27}\]

    C)  \[\frac{1}{6}\]                                  

    D)  \[\frac{1}{8}\]

    Correct Answer: D

    Solution :

                     \[\frac{N}{{{N}_{0}}}={{\left( \frac{1}{2} \right)}^{t/{{T}_{1/2}}}}\] Given: \[{{T}_{1/2}}=3\,h,\,\,t=9h\] \[\therefore \]  \[\frac{N}{{{N}_{0}}}={{\left( \frac{1}{2} \right)}^{9/3}}={{\left( \frac{1}{2} \right)}^{3}}\] \[\Rightarrow \]               \[\frac{N}{{{N}_{0}}}=\frac{1}{8}\] Activity \[=\left| \frac{-dN}{dt} \right|=N\lambda \] \[\therefore \]  \[\frac{A}{{{A}_{0}}}=\frac{N\lambda }{{{N}_{0}}\lambda }=\frac{N}{{{N}_{0}}}=\frac{1}{8}\]


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