If the fraction of the atoms of a radioactive material left after 120years is 1/64, what is the half-life of the material?
-
A.
24 years -
B.
20 years -
C.
10 years -
D.
2 years
Correct Answer: Option B
Explanation
1/64 is the usual fraction left of any radio active material after 4 half-lives, since 1/64 = (1/2)6
This implies that 6 half lives have elapsed.
Thus 6 half lives = 120 years
∴ 1 half life = 120/6 = 20 years