JEE Main & Advanced Physics Nuclear Physics And Radioactivity Question Bank Radioactivity

  • question_answer
    In a mean life of a radioactive sample        [MP PMT 2000, 03]

    A)            About 1/3 of substance disintegrates

    B)            About 2/3 of the substance disintegrates

    C)            About 90% of the substance disintegrates

    D)            Almost all the substance disintegrates

    Correct Answer: B

    Solution :

                       By using \[N={{N}_{0}}{{e}^{-\lambda t}}\] and \[t=\tau =\frac{1}{\lambda }\] Substance remains \[=N=\frac{{{N}_{0}}}{e}=0.37{{N}_{0}}\tilde{}\,\frac{{{N}_{0}}}{3}\] \ Substance disintegrated \[={{N}_{0}}-\frac{{{N}_{0}}}{3}=\frac{2{{N}_{0}}}{3}\]


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