JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumCalculation

JEE Main 25 July 2021, Shift 1, Physics Q5

Question 5 of 90 in this shift, Physics question 5 of 30, Section A.

Some nuclei of a radioactive material are undergoing radioactive decay. The time gap between the instances when a quarter of the nuclei have decayed and when half of the nuclei have decayed is given as : (where

\lambda

is the decay constant)

(1) $\frac{\ln\frac{3}{2}}{\lambda}$ Official answer
(2) $\frac{1}{2}\frac{\ln2}{\lambda}$
(3) $\frac{2\ln2}{\lambda}$
(4) $\frac{\ln2}{\lambda}$

Official answer

Option 1

NTA final key.

Chapter: Nuclei
Topic: Radioactive Decay
Idea tested: Statistical Decay Law

Same idea in other shifts

Asked 5× in all

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Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.