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Thread: Radioactive dating?

  1. #1 Radioactive dating? 
    New Member
    Join Date
    Sep 2009
    This is about radioactive dating and decay.
    So this is what I must do:
    There is 1 unit of radioactive uranium-238.
    It has a half-life of 4.5 billion years.
    After 4.5 billion years, half of the original unit of radioactive uranium-238 remains.
    Another 4.5 billion years later, one fourth of the original unit of uranium-238 remains.

    1. How long will it take a 100-atom sample of uranium-238 to decay half of this number?
    2. How much of a 100 atom sample will be left after 13.5 billion years?
    3. How long on average will it take a 100 atom sample of uranium-238 to decay to 25 atoms?
    4. A rock sample contains 200 atoms of uranium and 800 atoms of lead (lead is the decay product of uranium). When the rock formed, all the lead present was uranium. Approximately how long ago was the rock formed?

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  3. #2  
    Administrator KALSTER's Avatar
    Join Date
    Sep 2007
    South Africa

    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

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  4. #3  
    WYSIWYG Moderator marnixR's Avatar
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    Apr 2007
    Cardiff, Wales
    i can't believe you've given this set of questions any serious thought
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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