Question

Activity of radioactive element decreased to one third of original activity R₀ in 9 years. After further 9 years, its activity will be –

• A. R₀
• B. $\frac{2}{3}$R₀
• C. R₀ / 9
• D. R₀ / 9

Answer 1

Answer: (C)

R₀ / 9

Answer 2

A.P₁ =$\frac { 1 } { 3 }$, t₁ = 9 years, A.P₂ = ?, t₂ = 18 years

A.P₂ = = $\left( \frac { 1 } { 3 } \right) ^ { 18 / 9 }$ = $\left( \frac { 1 } { 3 } \right) ^ { 2 }$= $\frac { 1 } { 9 }$