Asked by notty
the isotope caesium-137 has a half life of 30 years how long will it take for the amount of this isotope in a sample of caesium to decay to 1/16th of its origional amount. thanks
amountremaining=oriinalamount(1/2)^time/timehalflife.
1/16= (1/2)^t/30
(1/2)^4= (1/2)^t/30
so t/30= 4
solve for t in years.
Another, but longer way, of solving the problem follows:
k=0.693/t<sub>1/2</sub>
solve for k. THEN,
ln(N<sub>o</sub>/N)=kt
where N<sub>o</sub> = original # atoms = 16
N = # atoms at some future time = 1
k is from above.
solve for t.
You should get the same answer either way.
amountremaining=oriinalamount(1/2)^time/timehalflife.
1/16= (1/2)^t/30
(1/2)^4= (1/2)^t/30
so t/30= 4
solve for t in years.
Another, but longer way, of solving the problem follows:
k=0.693/t<sub>1/2</sub>
solve for k. THEN,
ln(N<sub>o</sub>/N)=kt
where N<sub>o</sub> = original # atoms = 16
N = # atoms at some future time = 1
k is from above.
solve for t.
You should get the same answer either way.
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