JEE Main 2023 · PhysicsMultiple choiceSingle correctEasyApplication

JEE Main 11 April 2023, Shift 1, Physics Q33

Question 33 of 90 in this shift, Physics question 3 of 30, Section A.

Two radioactive elements A and B initially have same number of atoms. The half life of A is same as the average life of B. If

\lambda_A

and

\lambda_B

are decay constants of A and B respectively, then choose the correct relation from the given options.

(1) $\lambda_A \ln 2 = \lambda_B$
(2) $\lambda_A = \lambda_B \ln 2$ Official answer
(3) $\lambda_A = \lambda_B$
(4) $\lambda_A = 2\lambda_B$

Official answer

Option 2

NTA final key.

Chapter: Nuclei
Topic: Radioactive Decay
Idea tested: Mean Life Calculation

Same topic in other shifts

All Radioactive Decay questions

8 Apr 2026, Shift 2 · Q44Two radioactive substances A and B of mass numbers 200 and 212 respectively, shows spontaneous $\alpha$ -decay with same $Q$ value of 1…MediumSingle correct
4 Apr 2025, Shift 2 · Q42A radioactive material P first decays into Q and then Q decays to non-radioactive material R. Which of the following figure represents…MediumDiagram basedHas a figure
8 Apr 2023, Shift 2 · Q44A radio active material is reduced to 1/8 of its original amount in 3 days. If $8\times10^{-3}$ kg of the material is left after 5 days…MediumSingle correct
28 Jul 2022, Shift 1 · Q48The half life period of a radioactive substance is 60 days. The time taken for $\frac{7}{8}$ th of its original mass to disintegrate will…EasySingle correct
28 Jul 2022, Shift 1 · Q52A freshly prepared radioactive source of half life 2 hours 30 minutes emits radiation which is 64 times the permissible safe level. The…EasyNumerical value
29 Jun 2022, Shift 1 · Q33The activity of a radioactive material is $2.56 \times 10^{-3}$ Ci. If the half life of the material is 5 days, after how many days the…EasySingle correct

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 42 of the 174 JEE Main shifts held from 2017 to 2026.