Question

A heavy nucleus $Q$ of half-life $20$ minutes undergoes alpha-decay with probability of $60 \%$ and beta-decay with probability of $40 \%$. Initially, the number of $Q$ nuclei is $1000$. The number of alpha-decay of $Q$ in the first one hour is

• A. 50
• B. 75
• C. 350
• D. 525

Answer 1

Answer: (D)

525

Answer 2

Total no. of decays in 60 minutes
$=1000−1000(\frac{1}{2}​)^3=875$
So, no. of α -decay =875×0.6=525
The Correct answer is option (D): 525