Question 443186
Estimating the age of a fossil: A fossilized leaf contains 70% of its normal amount of carbon 14.
 How old is the fossil to the nearest year? Use 5600 years as the half life of carbon 14.
:
The radioactive decay formula A = Ao*2^(-t/h)
where
A = amt after t yrs
Ao = initial amt
h = half-life of substance
:
Assuming initial amt = 1 we have
1*2^(-t/5600) = .7
Using nat logs
ln(2^(-t/500)) = ln(.7)
log equiv of exponents
{{{-t/5600}}}*ln(2) = ln(.7)
{{{-t/5600}}} = {{{ln(.7)/ln(2)}}}
using a calc
{{{-t/5600}}} = -.51457
t = -.51457 * -5600
t = 2881.6 yrs to have 70% left of initial amt
:
:
Check solution on a calc; enter 2^(-2881.6/5600), results .7000