Question

The half-life o f ${}^{131}I$ is 8 days. Given a sample o f ${}^{131}I$ at time t=0, we can assert tha

• A. no nucleus will decay before t = 4 days
• B. no nucleus will decay before t = 8 days
• C. all nuclei will decay before ( = 16 days
• D. a given nucleus may decay at any time after ( = 0

Answer 1

Answer: (D)

Number of nuclei decreases exponentially
$N=N_0{e}^{-\lambda t}$
Therefore, decay process lasts upto $t=\propto$. Therefore, a given nucleus may decay at any time after t = 0.