VMMC VMMC Medical Solved Paper-2013

  • question_answer
    Suppose, 1 mg of radioactive substance is taken initially. After 2 h, it is found that 0.25 mg of the substance is left behind. The mean life of the substance is

    A) \[\frac{1}{0.693}h\]

    B)  \[0.693\times 2h\]

    C)  \[0.693\times \frac{1}{4}h\]

    D)  \[0.693\times 8h\]

    Correct Answer: A

    Solution :

     \[N={{N}_{0}}{{e}^{-\lambda t}}\] \[\frac{N}{{{N}_{0}}}={{e}^{-\lambda t}}\] \[\frac{1}{0.25}={{e}^{-\lambda t}}\] \[4={{e}^{-2\lambda }}\] \[{{\log }_{e}}4=-2\lambda \] \[\lambda =0.693/h\] Also mean-life =\[\frac{\text{1}}{\text{decay}\,\text{constant( }\!\!\lambda\!\!\text{ )}}\]


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