Re: Practical demonstration of a half-life

[LEHaskell@aol.com]

Two things I used to do for school kids:

1)  If you want to show a real radioactive decay, use thorium lantern mantles 
(if you can still find 'em).  Put on in a lab squeeze bottle and you'll catch 
the Rn-220 emanation.  To detect it we used an alpha probe with a 2x2 lucite 
chamber attached to the end.  Squeeze radon in through a small hole and watch 
the counts decay away.  I never tried it with a G-M probe, though I imagine 
it would work, although background counts might confuse things a bit.

2)  Put a bunch of coins heads up in a box.  Shake the box.  Coins which are 
tails up have decayed, those heads up are still "radioactive".  Seperate the 
"decayed" from the "active" and shake again.  Each shake is a "half-life".  
The trick is to point out that the total number of coins remains constant, 
only the state changes.
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