JEE Main 2019PhysicsNuclear PhysicsMediumMCQ

JEE Main 2019 — Nuclear Physics Question with Solution

JEE Main 2019 (10 Apr Shift 2)

Question

Two radioactive substances A and B have decay constants 5λ and λ respectively. At t=0, a sample has the same number of the two nuclei. The time taken for the ratio of the number of nuclei to become 1e2 will be

Choose an option

Show full solutionCorrect option: B
Correct answer
B12λ

Step-by-step explanation

Using the decay equation, N=N0e-λt
For radioactive substance A, N1=N0e-5λt ...........(i)
For radioactive substance B, N2=N0e-λt ............(ii)
From equation (i) and (ii)
N1N2=e-5λte-λt
1e2=e-4λt
4λt=2
Time taken, t=12λ

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About this question

This is a previous-year question from JEE Main 2019, 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.