Exponential Decay
Polonium, a radioactive element discovered by Marie Curie in 1898 and named after her native country Poland, decays exponentially.
If y0 grams of polonium are initially present , the number of grams y present after t days is given by function exponential
y = y0 e -0.05t
The graph of the function y = 5e -0.05t in the figure is the decreasing exponential curve that illustrates the exponential decay of 5 grams of polonium.
After 730 days we have
y = 5e (-0.05).(750) = 5e -3.65
which is approximately 0.13 grams of polonium left.