Question

Activity of a radioactive element decreased to one third of original activity I₀ in 9 years. After further 9 years. Its activity will be-

• A. I₀
• B. 2/3 I₀
• C. I₀/9
• D. I₀/6

Answer 1

Answer: (C)

I₀/9

Answer 2

I = I₀/2ⁿ, I₀/3 = I₀/2^9/T

I' = I₀/2^18/T =