BCECE Medical BCECE Medical Solved Papers-2004

  • question_answer
    A radioactive substance after 48 days remains 25% of initial then find disintegration constant:

    A)  \[2.89\times {{10}^{-2}}{{T}^{-1}}\]

    B)  \[3.89\times {{10}^{-3}}{{T}^{-1}}\]

    C)  \[4.89\times {{10}^{-2}}{{T}^{-1}}\]

    D)  none of these

    Correct Answer: A

    Solution :

    Key Idea: \[k=\frac{2.303}{t}\log \,\frac{{{N}_{0}}}{{{N}_{t}}}\] where t = time = 48 days \[{{N}_{0}}=\] Initial amount of radioactive substance       = 100 \[{{N}_{t}}=\] Initial amount of radioactive substance                          left after time t = 25 \[\therefore \] \[k=\frac{2.303}{48}\log \frac{100}{25}\]                 \[=0.0479\log 4=0.0479\times 0.6020\] \[=2.89\times {{10}^{-2}}T{{}^{-1}}\]


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