JCECE Medical JCECE Medical Solved Paper-2011

  • question_answer
    Let T be the mean life of a radioactive sample. 75% of the active nuclei present in the sample initially will decay in time

    A) \[2T\]

    B)  \[\frac{1}{2}(ln2)T\]

    C)  \[4T\]

    D)  \[2(ln2)T\]

    Correct Answer: D

    Solution :

     As \[\frac{N}{{{N}_{0}}}={{e}^{-\lambda t}}\] \[\frac{25}{100}={{e}^{-\lambda t}}=\frac{1}{4}\] or \[-\lambda t{{\log }_{e}}e=-{{\log }_{e}}4\] \[=-2{{\log }_{e}}2\] \[t=\frac{2{{\log }_{e}}2}{\lambda }\] Because mean life \[T=\frac{1}{\lambda }\] \[t=(2ln2)T\]


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