Question

Plutonium decays with half life of $24000$ years. If plutonium is stored for $72000$ years, the fraction of it that remains is

• A. $1/8$
• B. $1/3$
• C. $1/4$
• D. $1/2$

Answer 1

Answer: (A)

$1/8$

Answer 2

Here, $n=\frac{72000}{24000}=3, \frac{N}{N_{0}}=\left(\frac{1}{2}\right)^{n}=\left(\frac{1}{2}\right)^{3}=\frac{1}{8}$