Question 31

Question

If a radioactive isotope has a half-life of 20 hours, how many half-lives have occured after 80 hours have passed?

a
5
b
2
c
3
d
4

Answer 1

To determine how many half-lives have occurred after 80 hours, you simply divide the total time that has passed (80 hours) by the half-life of the isotope (20 hours):

\[ \text{Number of half-lives} = \frac{\text{Total time}}{\text{Half-life}} = \frac{80 \text{ hours}}{20 \text{ hours}} = 4 \]

So, the answer is:

d) 4