number of ^131 I nuclei remains, which also means that only 25% of the original mass of ^131 I
remains. Since the original dose contained 12 mg of ^131 I, only 3 mg remains after 16.1 days.4 . –λ
The expression n = n 0 e–λt is equivalent to n/n 0 = e–λt. Taking the natural logarithm of both sides
of the latter expression you find:ln(n/n 0 ) = –λt
From this expression it is clear that plotting ln(n/n 0 ) versus t will give a straight line of slope –λ.