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NEET AIPMT SOLVED PAPER SCREENING 2012

  • question_answer
    A mixture consists of two radioactive materials \[{{A}_{1}}\] and \[{{A}_{2}}\] with half lives of 20 s and 10 s respectively. Initially the mixture has 40 g of \[{{A}_{1}}\] and 160 g of \[{{A}_{2}}\]. The amount of the two in the mixture will become equal after

    A) 60 s          

    B)                        80 s                       

    C) 20 s                       

    D)        40 s

    Correct Answer: D

    Solution :

    For 40 g amount \[40\,g\xrightarrow[half-life]{20\,s}20\,g\xrightarrow[{}]{20\,s}10g\] For 160 g amount \[160\,g\xrightarrow{10\,s}80\,g\xrightarrow[{}]{10\,s}40g\] \[\xrightarrow[{}]{10\,s}20\,g\xrightarrow[{}]{10\,s}10g\] So, after \[40s\,{{A}_{1}}\] and \[\,{{A}_{2}}\]remains same.


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