Question

The half-life of $T{e}^{99}$ is 6h. The activity of $T{e}^{99}$ in a patient, 60 h after receiving an injection containing this radioisotope is at least 0.125 $\mu$ci. What was the minimum activity (in $\mu$ci) of the sample injected?

• A. 1.25
• B. 12.5
• C. 128
• D. 125

Answer 1

The correct option is C 128

Half life of sample, T = 6h
ge of sample t = 60h = 10T
No. of half lives n = 10
Activity A = $\frac{A_0}{2^n}\Rightarrow A_0=A{.2}^n=0.125\times 2^{10}=128\mu ci$