Question

Half life of ${}^{60}Co$ is $5.3$ years, the time taken for $99.9$% decay will be:

• A. $0.53$ years
• B. $53$ years
• C. $530$ years
• D. $5300$ years

Answer 1

Answer: (B)

$53$ years

$t_{99.9\%}=10t_{1/2}$
$=10\times 5.3=53years$