Half life question: The graph below shows the number of radioactive atoms present in four radioactive materials at different time intervals. Which of these materials has the shortest half-life?

A

Explanation:

Half life is the time it takes for a substance to reduce to half of the original composition. All the substances in graph start at 1000 particles and the half of thousand particles is 500. If you scan 500 and look at the X-axis for hours, we see it takes A the shortest amount of time (~3hrs) to reduce to half of original composition, whereas rest of them take more than that.