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

  • question_answer
    A sample of radioactive element has a mass of 10 gm at an instant t = 0.The approximate mass of this element in the sample after two mean lives is                          [CBSE PMT 2003]

    A)            2.50 gm                                  

    B)            3.70 gm

    C)            6.30 gm                                  

    D)            1.35 gm

    Correct Answer: D

    Solution :

                       \[M={{M}_{0}}{{e}^{-\lambda t}};\] given \[t=2\left( \frac{1}{\lambda } \right)\]                    \[\Rightarrow M=10{{e}^{-\lambda \left( \frac{2}{\lambda } \right)}}=10{{\left( \frac{1}{e} \right)}^{2}}\Rightarrow M=1.35\ gm\]


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