Chhattisgarh PMT Chhattisgarh PMT Solved Paper-2006

  • question_answer
    If No is the original mass of the substance of half-life period \[{{T}_{1/2}}=5\] yr, then the amount of substance left after 15 yr is

    A)  \[{{N}_{0}}\text{/8}\]                                  

    B) \[{{N}_{0}}\text{/16}\]

    C)  \[{{N}_{0}}\text{/2}\]                                  

    D)  \[{{N}_{0}}\text{/4}\]

    Correct Answer: A

    Solution :

    \[{{T}_{1/2}}=5yr,\] \[t=15yr\] \[\therefore \]  Number of half-lives \[(n)=\frac{t}{{{T}_{1/2}}}\]                                                 \[=\frac{15}{5}=3\] The amount of substance left undecayed.                 \[N={{N}_{0}}{{\left( \frac{1}{2} \right)}^{n}}\]                 \[={{N}_{0}}{{\left( \frac{1}{2} \right)}^{3}}=\frac{{{N}_{0}}}{8}\]


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