JEE Main 2021PhysicsNuclear PhysicsMediumMCQ

JEE Main 2021 — Nuclear Physics Question with Solution

JEE Main 2021 (25 Feb Shift 1)

Question

Two radioactive substances X and Y originally have N1 and N2 nuclei respectively. Half life of X is half of the half life of Y. After three half lives of Y, number of nuclei of both are equal. The ratio N1N2 will be equal to :

Choose an option

Show full solutionCorrect option: B
Correct answer
B81

Step-by-step explanation

Tx=t;Ty=2t

3Ty=6t,

N1'=N2'

N1e-λ16t=N2e-λ26t

N1 N2=eλ1-λ26t=e1t-12t×6tln2=eln23=eln8=8

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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.