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Topic: half life  (Read 3570 times)

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Offline naz86

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half life
« on: July 19, 2007, 06:03:17 PM »
hi, i wonder if anyone can help me, or at least point me into the right direction.

a half life uranium istope23492U is 245 000 years old,
wht percentage of this material will be left in 980 000 years?

all i knw is that
245000 x 2 = 490000
which is how old the uranium is....i think.
after this, i dnt knw wht to do.. someone pls help
« Last Edit: July 19, 2007, 06:09:52 PM by Borek »
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Offline Borek

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Re: half life
« Reply #1 on: July 19, 2007, 06:10:43 PM »
Not [ sup][ 234/sup] but [ sup]234[ /sup] (without spaces).
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Offline Yggdrasil

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Re: half life
« Reply #2 on: July 19, 2007, 06:39:41 PM »
If the half-life of an isotope is x years, then after x years, half of the sample will have decayed.

So, lets say you start with 100g of uranium-234.  After 245000 years, how much will be left?  After 980000 years, how much will be left?
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Offline sdekivit

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Re: half life
« Reply #3 on: July 20, 2007, 03:35:02 AM »
you'll probably know the formula N(t) = N(0) * (1/2)t / t1/2 with N = amount of particles, t = time and t1/2 = half-life

then you also know that N(t)/N(0) = (1/2)t/t1/2 and from this ratio you calculate the percentage that is left after t years
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