• Half life period of 53 I 125 is 60 days. What percentage of the original radioactivity would be present after 180 days?
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    In one half life, half (i.e., 50%) of the original content is left and the rest decays.

    In 60 days, 50% of original content is left.

    In 120 days (2 half lives), 25% of original content (50% of content left after 1 half live, i.e. 50% of 50%) is left.

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    In one half life, half (i.e., 50%) of the original content is left and the rest decays.

    In 60 days, 50% of original content is left.

    In 120 days (2 half lives), 25% of original content (50% of content left after 1 half live, i.e. 50% of 50%) is left.

    and in 180 days (3 half lives), 12.5% of original content is left.

    i.e. 1/8th of original quantity is left after 3 half lives.

    Approved by eNotes Editorial Team