JEE Main & Advanced AIEEE Solved Paper-2002

  • question_answer
    If \[{{N}_{0}}\] 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   AIEEE  Solved  Paper-2002

    A) \[\frac{{{N}_{0}}}{8}\]   

    B)                           \[\frac{{{N}_{0}}}{16}\]                    

    C)           \[\frac{{{N}_{0}}}{2}\]                      

    D)           \[\frac{{{N}_{0}}}{4}\]

    Correct Answer: A

    Solution :

    \[{{N}_{0}}\] is the initial amount of substance and N is the amount left after decay. Thus,                        \[N={{N}_{0}}{{\left( \frac{1}{2} \right)}^{n}}\]              \[n=\] number of half-lives \[=\frac{t}{{{t}_{1/2}}}=\frac{15}{3}=3\]              Therefore,          \[N={{N}_{0}}{{\left( \frac{1}{2} \right)}^{3}}=\frac{{{N}_{0}}}{8}\]


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