Physics · Nuclear Physics

JEE Advanced 2021 — Paper 1 — Question 3

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

Answer: D

Total no. of decays in 60 minutes $=1000-1000\left(\frac{1}{2}\right)^{3}=875$

So, no. of $\alpha$ -decay $=875 \times 0.6=525$

Answer key and solution verified before publishing.

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