J & K CET Engineering J and K - CET Engineering Solved Paper-2010

  • question_answer
    The fraction of a sample of radioactive nuclei that remains undecayed after one mean life is

    A)  \[\frac{1}{e}\]

    B)  \[1-\frac{1}{e}\]

    C)  \[\frac{1}{{{e}^{2}}}\]

    D)  \[1-\frac{1}{{{e}^{2}}}\]

    Correct Answer: B

    Solution :

    By using \[N={{N}_{0}}{{e}^{-\lambda t}}\] and average life time, \[t=\frac{1}{\lambda }\] So,    \[N={{N}_{0}}\,{{e}^{-\lambda \times 1\lambda }}={{N}_{0}}{{e}^{-1}}\] \[\Rightarrow \] \[\frac{N}{{{N}_{0}}}={{e}^{-1}}=\frac{1}{e}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner