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2 radioactive balls

  1. Oct 4, 2011 #1
    There are 2 radioactive balls, which have the same radius and the same weight. They are covered with absorbing layer. They are made of diffrent materials, with other half-life. What is the easiest way to recognise which is which?
    I had searched for the answer for a longer time and could not find out. Please for help.
     
  2. jcsd
  3. Oct 4, 2011 #2
    What do you mean by an absorbing layer? Do you mean the layer absorbs all of the radiated particles and energy from the radioactivity?
     
  4. Oct 4, 2011 #3

    sophiecentaur

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    You could, in principle, measure a change in densities somehow? ( Hint.)
     
  5. Oct 4, 2011 #4
    If you had the 2 balls with different levels of radiactivity immersed ( frak - I had to look up how to spell that word ) in seperate baths of water in inslolated containers each with thermal instrumentation, could you devise a way to tell them apart?
     
  6. Oct 5, 2011 #5
    thank you very much. that's a great idea to measure their densities or temperatures. i think, that one with density is the easiest one. you put them in water and the ball which has longer half-life would move down faster.
     
    Last edited: Oct 5, 2011
  7. Oct 5, 2011 #6
    yes.
     
  8. Oct 5, 2011 #7

    sophiecentaur

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    But remember, the problem, I think, demands that all products of the reaction stay within the ball. So how would you measures density change and 'which' densities would change?
     
  9. Oct 5, 2011 #8

    Matterwave

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    I vote for spinning the ball. If there is a layer (like skin) absorbing the radiated particles, then the moment of inertia of the balls should change at different rates.
     
  10. Oct 5, 2011 #9

    sophiecentaur

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    Go for it my son.
     
  11. Oct 5, 2011 #10
    My g/f says I have two radioactive balls. ;-)
     
    Last edited: Oct 5, 2011
  12. Oct 5, 2011 #11

    sophiecentaur

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    How fast are they decaying?
     
  13. Oct 5, 2011 #12
    > How fast are they decaying?

    Pretty fast these days. The interesting thing is that the decay rate is highly non-linear lately. I observed no decay in the first 20 years, a linear decay in the next ten years, somewhat of a geometric rate in years 30- 40, but since year 40 the rate appears to be exponential.

    I have no rational explanation for my observations.
     
  14. Oct 5, 2011 #13

    sophiecentaur

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    Use it or lose it my friend. No reason for things to fizzle out before the age of ninety!
     
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