JEE Main 2022 · PhysicsNumerical answerNumerical valueEasyCalculation

JEE Main 29 June 2022, Shift 2, Physics Q58

Question 58 of 90 in this shift, Physics question 28 of 30, Section B.

The half life of a radioactive substance is 5 years. After

x

years a given sample of the radioactive substance gets reduced to 6.25% of its initial value.The value of

x

is ________

Official answer

NTA final key.

Chapter: Nuclei
Topic: Radioactive Decay
Idea tested: Fractional Remainder Shortcut

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
10 Apr 2023, Shift 1 · Q56The decay constant for a radioactive nuclide is $1.5\times10^{-5}\,s^{-1}$ . Atomic weight of the substance is 60 g mole $^{-1}$ , (…EasyNumerical value
10 Apr 2023, Shift 2 · Q44The half life of a radioactive substance is T. The time taken, for disintegrating $\frac{7}{8}$ th part of its original mass will be:EasySingle correct
11 Apr 2023, Shift 1 · Q33Two 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 $\lambda_A$ …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 108 of the 174 JEE Main shifts held from 2017 to 2026.