JEE Main 2021PhysicsNuclear PhysicsHardMCQ

JEE Main 2021 — Nuclear Physics Question with Solution

JEE Main 2021 (16 Mar Shift 2)

Question

Calculate the time interval between 33% decay and 67% decay if half-life of a substance is 20 min.

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Show full solutionCorrect option: B
Correct answer
B20 min

Step-by-step explanation

N1=N0e-λt1

N1 N0=e-λt1

0.67=e-λt1

ln0.67=-λt1

 N2=N0e-λt2

N2 N0=e-λt2

0.33=e-λt2

ln0.33=-λt2

ln0.67-ln0.33=λt1-λt2

λt1-t2=ln0.670.33

λt1-t2≅ln2

t1-t2≃ln2λ=t1/2

Half life =t1/2=20 minutes.

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About this question

This is a previous-year question from JEE Main 2021, covering the Nuclear Physics chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.