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NEET Physics Nuclear Physics And Radioactivity NEET PYQ-Nuclear Physics

  • question_answer
    A mixture consists of two radioactive materials \[{{A}_{1}}\] and \[{{A}_{2}}\] with half-lives of 20s and 10s 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                                                                                 [AIPMT (S) 2012]

    A)  60 s                

    B)       80 s

    C)  20 s        

    D)  40 s

    Correct Answer: D

    Solution :

    For 40 g amount
    \[40\,g\xrightarrow[\text{half-life}]{20\,s}20\,g\xrightarrow[{}]{20\,s}10g\]
    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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