MGIMS WARDHA MGIMS WARDHA Solved Paper-2003

  • question_answer
    A radioactive substance containing N atoms emits \[n\,\alpha \]-particles per second, Half-life of the substance is :

    A) \[\frac{N}{n}\sec \]

    B) \[\frac{n}{N}\sec \]

    C) \[\frac{0.693n}{N}\sec \]                             

    D) \[\frac{0.693N}{n}\sec \]

    Correct Answer: D

    Solution :

    From decay law, \[-\frac{dN}{dt}\propto N\] Or           \[-\frac{dN}{dt}=\lambda N\] Here:-   \[-\frac{dN}{dt}=n\](\[\alpha -\]particles per second) and N = initial value of substance \[\therefore \]  \[n=\lambda N\]                                 \[\lambda =\frac{n}{N}\] \[\therefore \]Half-life \[{{T}_{1/2}}=\frac{0.693}{\lambda }\sec \]                 \[{{T}_{1/2}}=\frac{0.693N}{n}\sec \]


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