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Question: Answered & Verified by Expert
The half of a radioactive substance is 25 minutes The time between $50 \%$ decay and $87.5 \%$ decay of the substance will be
PhysicsNuclear PhysicsJEE Main
Options:
  • A 75 min
  • B $25 \mathrm{~min}$
  • C $37.5 \mathrm{~min}$
  • D $50 \mathrm{~min}$
Solution:
1689 Upvotes Verified Answer
The correct answer is: $50 \mathrm{~min}$
For $50 \%$ decay, time is equal to one half-life.
For $87.5 \%$ decay, time is three half - lives.
$\therefore$ Time interval $\Delta \mathrm{t}=2$ half - lives.
$\Delta t=2 \times 25 \mathrm{~min}=50 \mathrm{~min}$

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