MGIMS WARDHA MGIMS WARDHA Solved Paper-2003

  • question_answer
    In a sample of radioactive substance, what percentage decays in one mean life time?

    A) 69.3%                                   

    B) 63%

    C) 50%                                       

    D) 36%           

    Correct Answer: B

    Solution :

    From the law of Rutherford and Soddy,  we have \[\frac{N}{{{N}_{0}}}={{e}^{-\lambda t}}\] But mean life \[T=\frac{1}{\lambda }\] \[\therefore \]  \[\frac{N}{{{N}_{0}}}={{e}^{-t/T}}\] At           \[t=T\]                 \[\frac{N}{{{N}_{0}}}={{e}^{-1}}=\frac{1}{e}\]                 \[=0.37\]              Therefore, percentage decay\[=1-0.37\] \[=0.63=63%\]


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