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NEET Sample Paper NEET Sample Test Paper-82

  • question_answer
    A radioactive element has a half-life of 12.5 years against beta decay. The fraction of a sample of element that will remain undecayed after 25 years is

    A)  \[\frac{1}{2}th\]                       

    B)  \[\frac{1}{4}th\]

    C)  \[\frac{1}{8}th\]                       

    D)  None of these

    Correct Answer: B

    Solution :

    As,   \[\frac{N}{{{N}_{0}}}={{\left( \frac{1}{2} \right)}^{\frac{t}{{{t}_{1/2}}}}}\Rightarrow \,\,\frac{N}{{{N}_{0}}}={{\left( \frac{1}{2} \right)}^{\frac{25}{12.5}}}\] \[\frac{N}{{{N}_{0}}}=\frac{1}{4}\,\,\,\Rightarrow \,\,\,\,N\,\,=\,\,\frac{{{N}_{0}}}{4}\]


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