JEE Main & Advanced Physics Nuclear Physics And Radioactivity Question Bank Self Evaluation Test - Nuclei

  • question_answer
    The activity of a radioactive sample is measured as \[{{N}_{0}}\] counts per minute at t=0 and \[{{N}_{0}}/e\] counts per minute at t=5 minutes. The time (in minutes) at which the activity reduces to half its value is

    A)  \[{{\log }_{e}}2/5\]

    B)  \[\frac{5}{{{\log }_{e}}2}\]

    C)  \[5{{\log }_{10}}2\]

    D)  \[5{{\log }_{e}}2\]

    Correct Answer: D

    Solution :

    [d] \[N={{N}_{0}}{{e}^{-\lambda t}}\] Here, \[t=5\]minutes \[\frac{{{N}_{0}}}{e}={{N}_{0}}.{{e}^{-5\lambda }}\,\,\,\,\,\,\,\,\,\,\Rightarrow \,\,\,\,\,\,\,\,5\lambda =1,\,\,\,\lambda =\frac{1}{5},\] Now,       \[{{T}_{1/2}}=\frac{\ell n2.}{\lambda }=5\,\,\ell n2\]


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