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Hello,I'm revising half-life for GCSE and have come across some

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  1. Nov 7, 2012 #1
    Hello,
    I'm revising half-life for GCSE and have come across some questions regarding fractions.

    For example, "what fraction of the original nuclei will still be unstable after 5 half-lives?"

    Am I right in thinking it would be 1/20 as 1/2 x 5 = 1/20 or is that too simple?

    Thanks,
    Molly
     
  2. jcsd
  3. Nov 7, 2012 #2

    SammyS

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    Re: Half-Life

    Yes, that's too simple ... and how is (1/2) × 5 = 1/20 ?

    Think about it.

    After a time of one half-life, 1/2 of the original nuclei remain unchanged.


    After a time of an additional half-life, 1/2 of that 1/2 of the original nuclei remain unchanged. This is a total time of two half-lives and 1/4 of the original nuclei remain unchanged.

    Etc.
     
  4. Nov 7, 2012 #3
    Re: Half-Life

    Yeah, thank you I just realised I was being stupid. It's 1/32 right?
     
  5. Nov 7, 2012 #4

    SammyS

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    Re: Half-Life

    Right ! I mean, right, it's 1/32, not right about the other thing!
     
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