Suppose a laboratory has a 30 g sample of polonium-210. The half-life of polonium-210 is about 138 days How many half-lives of polonium-210 occur in 1104 days? How much polonium is in the sample 1104 days later?
This is an easy half-life calculation because it involves an exact integer of half-lives. 1,104 days is precisely 8 half-lives. After each half-life, one half of the original remains. So, after 8 half-lives you will have 1 / 2^8 of the original material left. So we start with 30 grams and 1 / 2^8 =
0.00390625. We are therefore left with (30 *
0.00390625) or
0.1171875 grams of the original 30 grams of polonium.
