The exponential growth function is
.
Consider the half-life of carbon 14 is
years.
Hence, time period is
and 
Substitue all the values.
\

Apply natural logarithm on each side.
\



There,the decay constant is
.
A fossilized leaf contains
of its normal amount of carbon 14.
Find the age of the fossil.
\
and
.
Susbtitute all the values in
.


Take natural logarithm on each side.
\


years.
Therefore, The age of the fossil is
years.
The age of the fossil is
years.