Question

The activity of a radioactive sample is 1.6 curie and its half-life is 2.5 days. Its activity after 10 days will be.

• A. 0.8 curie
• B. 0.4 curie
• C. 0.1 curie
• D. 0.16 curie

Answer 1

Answer: (C)

0.1 curie

Answer 2

Number of half lives $n = \frac{10}{2.5} = 4$

⇒ $\frac{A}{A_{0}} = \frac{N}{N_{0}} = \left( \frac{1}{2} \right)^{n} \Rightarrow A = 1.6 \times \left( \frac{1}{2} \right)^{4} = 0.1\mspace{6mu} curie$