Question

If half life of a radioactive element is 3 hours, after 9 hours its activity becomes.

• A. 1/9
• B. 1/27
• C. 1/6
• D. 1/8

Answer 1

Answer: (D)

1/8

Answer 2

By using $A = A_{0}\left( \frac{1}{2} \right)^{\frac{t}{T_{1/2}}}$ ⇒ $\frac{A}{A_{0}} = \left( \frac{1}{2} \right)^{9/3} = \frac{1}{8}$