Graph titled "Nuclear Decay." Horizontal axis reads Time. Vertical axis reads Radioisotope Remaining and is given in percentages. The horizontal axis consists of marks in terms of half lives, beginning at 0 and moving from left to right for 1 half-life, 2 half-lives, 3 half-lives, and then the graph ends at 4 half-lives. The vertical axis begins at 0 at the bottom and ranges up to 100. The line on the graph begins at 100 on the vertical axis and gradually declines all the way below 3 half-lives. As the line passes each half-life marker, the graph indicates the amount of idodine and xenon remaining.