Question

If $N_{0}$ is the original mass of the substance of half life period $T_{1/2} = 5$ years, then the amount of substance left after 15 years is.

• A. $N_{0}/8$
• B. $N_{0} ⥂ / ⥂ 16$
• C. $N_{0} ⥂ / ⥂ 2$
• D. $N_{0} ⥂ / ⥂ 4$

Answer 1

Answer: (A)

$N_{0}/8$

Answer 2

$N = N_{0}\left( \frac{1}{2} \right)^{\frac{t}{T_{1/2}}} = N_{0}\left( \frac{1}{2} \right)^{\frac{15}{5}} = \frac{N_{0}}{8}$.