Suppose that at some time a particular sample of radioactive material contains N radioactive atoms (e.g., N might be 1 billion radioactive atoms). How many radioactive atoms will be left after 3 half-lives have passed?
A) 1/6 N
B) 1/8 N
C) 0
D) 1/2 N

Question

Quizplus · Accepted Answer

After each half-life, the number of radioactive atoms is reduced by half. Therefore, after 3 half-lives, the amount of radioactive material left would be N/2 (after the first half-life) then (N/2)/2 = N/4 (after the second half-life), and finally (N/4)/2 = N/8 (after the third half-life).

Suppose That at Some Time a Particular Sample of Radioactive