N=N₀exp(-ln2•t/T)
ln{N/N₀) = -ln2•t/T
t= - ln{N/N₀)•T/ln2=
= - ln(3.25/26) •713•10⁶/ln2 =
= 2.14•10⁹ years
The half-life of uranium-235 is 713 million years. Suppose a fossil originally had 26 grams of uranium-235. A geologist had the fossil tested and found that it now has only 3.25 grams of uranium-235.
Approximately how old is the fossil?
1 answer