The graph shows the activity R as a function of the time t for three radioactive samples. Rank the samples according to their half-lives, shortest to longest.
A) 1, 2 ,3
B) 1, 3, 2
C) 2, 1, 3
D) 2, 3, 1
E) 3, 1, 2

Question

The graph shows the activity R as a function of the time t for three radioactive samples. Rank the samples according to their half-lives, shortest to longest. 
A) 1, 2 ,3 
B) 1, 3, 2 
C) 2, 1, 3 
D) 2, 3, 1 
E) 3, 1, 2

Quizplus · Accepted Answer

The half-life of a radioactive material is the time it takes for half of the material to decay. The graph shows that Sample 2 reaches half of its activity at around 4 hours, while Sample 1 reaches half of its activity at around 6 hours. Sample 3, however, takes more than 8 hours to reach half of its activity. Therefore, the order of half-lives from shortest to longest is Sample 2, Sample 1, Sample 3. This corresponds to Choice C.

The Graph Shows the Activity R as a Function of the Time