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