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CMC Medical CMC-Medical VELLORE Solved Paper-2010

  • question_answer
    The half-life of the isotope\[_{11}N{{a}^{24}},\]is 15 h. How much time does it take for\[\frac{7}{8}\]th of a same of this isotope to decay?

    A)  75 h                                      

    B)  65 h

    C)  55 h                                      

    D)  45 h

    E)  None of these

    Correct Answer: D

    Solution :

                    Undecayed isotope\[=1-\frac{7}{8}=\frac{1}{8}\] \[\frac{N}{{{N}_{0}}}={{\left( \frac{1}{2} \right)}^{t/T}}\] \[\frac{1}{8}={{\left( \frac{1}{2} \right)}^{t/15}}\] \[\frac{t}{15}=3\] \[t=45\,h\]


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