If the fraction of the atoms of a radioactive material left after 120 years 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 = 20 years

Explanation

Given amount remaining = ¹/₆₄
= ¹/₆₄= (½)⁶
∴ = ^120years/₆ = 20 years

⇒ T½ = 20 years