RAJASTHAN ­ PET Rajasthan PET Solved Paper-2004

  • question_answer
    During mean life of a radioactive element, the fraction that disintegrates is

    A)  \[e\]

    B)  \[\frac{1}{e}\]

    C)  \[\frac{e-1}{e}\]

    D)  \[\frac{e}{e-1}\]

    Correct Answer: C

    Solution :

     \[N={{N}_{0}}{{e}^{-\lambda t}}\] and      average year\[t=\frac{1}{\lambda }\] \[\therefore \] \[N={{N}_{0}}{{e}^{-\lambda \times 1/\lambda }}={{N}_{0}}{{e}^{-1}}\] \[\frac{N}{{{N}_{0}}}=\frac{1}{e}\] Reduced part \[=1-\frac{N}{{{N}_{0}}}=1-\frac{1}{e}=\frac{e-1}{e}\]


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