BVP Medical BVP Medical Solved Paper-2004

  • question_answer
    The half-life of a radioactive substance is 40 years. How long will it take to reduce to one fourth of its original amount and what is the value of decay constant?

    A)  40 year, 0.9173/year

    B)  90 year, 9.017/year

    C)  80 year, 0.0173/year

    D)  none of these

    Correct Answer: C

    Solution :

                                                               Here:  \[{{T}_{1/2}}=40\] years,  \[\frac{N}{{{N}_{0}}}=\frac{1}{4}\] From relation \[\frac{N}{{{N}_{0}}}={{\left( \frac{1}{2} \right)}^{t/40}}\] or            \[\left( \frac{1}{4} \right)={{\left( \frac{1}{2} \right)}^{t/40}}\] or            \[{{\left( \frac{1}{2} \right)}^{2}}={{\left( \frac{1}{2} \right)}^{t/40}}\] Hence,  \[\frac{t}{40}=2\]or t = 80 year Decay constant \[\lambda =\frac{0.693}{{{T}_{1/2}}}=\frac{0.693}{40}=0.0173year\]


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