Easy MCQ +4 / -1 PYQ · JEE Mains 2022

The disintegration rate of a certain radioactive sample at any instant is 4250 disintegrations per minute. 10 minutes later, the rate becomes 2250 disintegrations per minute. The approximate decay constant is :

$\left(\right.$Take $\left.\log _{10} 1.88=0.274\right)$

  1. A $0.02 \min ^{-1}$
  2. B $2.7 \min ^{-1}$
  3. C $0.063 \min ^{-1}$ Correct answer
  4. D $6.3 \min ^{-1}$

Solution

<p>${A_0} = 4250$</p> <p>$A = 2250 = {A_0}{e^{ - \lambda t}}$</p> <p>$\Rightarrow {{2250} \over {4250}} = {e^{ - \lambda t}}$</p> <p>$\Rightarrow \lambda (10) = \ln \left( {{{4250} \over {2250}}} \right)$</p> <p>$\lambda (10) = 0.636$</p> <p>$\lambda = 0.063$</p>

About this question

Subject: Physics · Chapter: Atoms and Nuclei · Topic: Radioactivity

This question is part of PrepWiser's free JEE Main question bank. 184 more solved questions on Atoms and Nuclei are available — start with the harder ones if your accuracy is >70%.

Drill 25 more like these. Every day. Free.

PrepWiser turns these solved questions into a daily practice loop. Chapter-wise drills, full mocks, AI doubt chat. No auto-renew.

Start free →