Uttarakhand PMT Uttarakhand PMT Solved Paper-2011

  • question_answer
    A certain radioactive substance has a half-life of 5 years. Thus, for a nucleus in a sample of the element, the probability of decay in 10 years is

    A)  50%            

    B)  75%

    C)  100%           

    D)  60%

    Correct Answer: B

    Solution :

     Number of half-lives, \[n=\frac{10}{5}=2\] Remaining amount, \[N={{N}_{0}}{{\left( \frac{1}{2} \right)}^{n}}\] \[={{N}_{0}}{{\left( \frac{1}{2} \right)}^{2}}=\frac{{{N}_{0}}}{4}\] \[\frac{N}{{{N}_{0}}}=\frac{1}{4}\times 100=25%\] Probability of decay \[=(100-25)%=75%\]


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