Question

Half-life of a radioactive element X is 4 days. The probability that a nucleus will decay in two half-lives is

• A. $\frac{1}{4}$
• B. $\frac{3}{4}$
• C. $\frac{1}{2}$
• D. $1$

Answer 1

Answer: (B)

$\frac{3}{4}$

After two half-lives $\frac{1}{4}th$ fraction of nuclei will remain undecayed.
$\frac{3}{4}th$ fraction will decay, probability that a nucleus decays in two half lives is $\frac{3}{4}th$.