DUMET Medical DUMET Medical Solved Paper-2002

  • question_answer
    The half-life of radium is 1600 yr. What fraction of sample of radium will be disintegrated after 6400 yr?

    A)  \[\frac{13}{16}\]

    B)  \[\frac{1}{16}\]

    C)  \[\frac{8}{17}\]

    D)  \[\frac{15}{16}\]    

    Correct Answer: D

    Solution :

    From Rutherford-Soddys law, the fraction of sample remains undecayed after n half-lives is \[\frac{N}{{{N}_{0}}}={{\left( \frac{1}{2} \right)}^{n}}\]  where \[{{N}_{0}}\] is original number of atoms. \[\therefore \] \[n=\frac{6400}{1600}=4\] \[\therefore \] \[\frac{N}{{{N}_{0}}}={{\left( \frac{1}{2} \right)}^{n}}={{\left( \frac{1}{2} \right)}^{4}}=\frac{1}{16}\] The fraction of sample disintegrated is \[=1-\frac{1}{16}=\frac{15}{18}\]


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