Question

The half life period of a radioactive element is $140$ days. After $560$ days the remaining amount of the element would be:

• A. $1/2$ of the original amount
• B. $1/4$ of the original amount
• C. $1/8$ of the original amount
• D. $1/16$ of the original amount

Answer 1

Answer: (D)

$1/16$ of the original amount

$N_t=N_o(\frac{1}{2}{)}^{t/t_{1/2}}$

$N_t=N_o(\frac{1}{2}{)}^{560/140}=N_o(\frac{1}{2}{)}^4=N_o\left(\frac{1}{16}\right)$