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BHU PMT BHU PMT (Screening) Solved Paper-2006

  • question_answer
    A radioactive substance decays to,\[\frac{3}{4}\]th of its original value in 30 min. The half-life of the substance is:

    A)  60 min                                 

    B)  5 min

    C)   7.5mm                               

    D)  15 min

    Correct Answer: D

    Solution :

                     \[\lambda =\frac{2.303}{t}\log \frac{{{N}_{0}}}{N}\] \[=\frac{2.303}{30}\log \frac{1}{1-\frac{3}{4}}=\frac{2.303}{30}\log 4\]                 \[=0.0462\,{{\min }^{-1}}\] \[{{t}_{1/2}}=\frac{0.693}{\lambda }=\frac{0.693}{0.0462}\]


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