NEET Sample Paper NEET Sample Test Paper-33

  • question_answer
    In a sample of radioactive material, what percentage of the initial number of active nuclei will decay during mean life:

    A)  37%             

    B)  87%

    C)  63%             

    D)  69.3%

    Correct Answer: A

    Solution :

    According to Rutherford-soddy law \[N={{N}_{0}}{{e}^{-\lambda \,r}}\] Where No is initial number of atoms present \[\lambda \] the decay constant and t the mean life-time. Applying the formula \[\tau =\frac{1}{\lambda },\]we have, \[N={{N}_{0}}{{e}^{-\lambda \tau }}={{N}_{0}}{{e}^{-1}}=\frac{{{N}_{0}}}{e}\] Percentage decayed \[=\frac{{{N}_{0}}-N}{{{N}_{0}}}\times 100\] \[=\frac{\frac{{{N}_{0}}-{{N}_{0}}}{e}}{{{N}_{0}}}\times 100=63%\]


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