Halflife or something like it

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Half-life or something like it

• Adventures in presenting exponential decay
• Kenneth Cecire, Hampton University
• American Association of Physics Teachers Summer
  Meeting
• California State University, Sacramento

This work is supported in part by the U.S.
Department of Energy Office of Science and the
National Science Foundation.
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• Good idea Students learn about exponential
  decay, half-life, and lifetime

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• Bad idea students get hands-on experience
  with ionizing radiation

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So we do the pennies lab

• Shows half-life clearly
• Clean exponential decay
• Good chance to use pooling of student results to
  get large data sets

• Shows half-life of one shake too clearly
• Costs at least 50 cents to do right

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• The licorice method works as well, lends
  itself to an instant graph, and comes in several
  flavors.but still has the problem of an obvious
  half-life

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• What determines half-life (or particle lifetime)?
• How do we show itbut make it something that can
  be investigated?
• How can we change half-life by changing
  parameters?

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• The answer is really a bit of a crap shoot

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Calculated half-life 4.19 shakes
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• Time to playHowd they get those results?

Calculated half-life 100.46 s
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• Hint

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• Another hint

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Calculated half-life 22.88 s

• How theyd get this?

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• Hint

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• More hints

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• And what about this?

Calculated Half-life 1.94 s Calculated Lifetim
e 2.80 s
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• Hint

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• Why do we care? Lets count the ways
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