VMMC VMMC Medical Solved Paper-2004

  • question_answer
    Plutonium-decays with a half-life of 24000 years. If plutonium is stored for 72000 years, then the fraction of plutonium that remains, is

    A) \[\frac{1}{8}\]                   

    B)        \[\frac{1}{4}\]                   

    C)         \[\frac{1}{3}\]                  

    D)        \[\frac{1}{2}\]

    Correct Answer: A

    Solution :

    The decay constant \[\lambda =\frac{0.693}{{{T}_{1/2}}}=\frac{0.693}{24000}=2.89\times {{10}^{-5}}\] Hence, the fraction of plutonium left is \[\frac{N}{{{N}_{o}}}={{e}^{-\lambda t}}={{e}^{(-2.89\times {{10}^{-5}})\times 72000}}\] \[={{e}^{-2.08}}=\frac{1}{{{e}^{2.08}}}=\frac{1}{8}\]


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