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NEET Sample Paper NEET Sample Test Paper-7

  • question_answer
    A half life of \[^{215}At\] is \[100\mu s\]is. The time taken for the radioactive of a sample of \[^{215}At\] to decay to 1/16 of its initial value is:

    A)  \[400\,s\]                    

    B)  \[6.3\,s\]

    C)   \[40\,s\]                     

    D)  \[300\,s\]        

    Correct Answer: A

    Solution :

    As,               \[R={{R}_{0}}{{\left( \frac{1}{2} \right)}^{n}}\] Given,           \[R=\frac{{{R}_{0}}}{16}\]                                 \[\frac{{{R}_{0}}}{16}={{R}_{0}}{{\left( \frac{1}{2} \right)}^{n}}\] On solving, \[n=4\] Total time  \[t=n.\] \[{{t}_{1/2}}\]                 \[=4\times (100)=400s\]


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