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Saturday, 31 October

JEE Main · Physics · Nuclei

Integer Half-Life Shortcuts

JEE Main asked Integer Half-Life Shortcuts 7 times in 6 of the 108 shifts Lumi analysed, in 2021 and 2022. It belongs to Radioactive Decay, in Nuclei (Physics). The longest wait between two years asking it was 1 year. In 2021 and 2022 it came in more than one shift of the same year.

Updated 2026-10-24

Times asked
7
in 6 shifts
Years
2 of 8
First asked
2021
last in 2022
Pattern
Occasional
across the analysed shifts

Questions on this idea a shift, by year

2017–2026. Asked in 2021 and 2022. Years differ in how many shifts Lumi analysed, so each year is scaled to one shift of 25 Physics questions.

00.10.20’170’200.07’210.17’220’230’240’250’26

Raw count: 2017: 0 in 1 shift · 2020: 0 in 12 shifts · 2021: 2 in 24 shifts · 2022: 5 in 24 shifts · 2023: 0 in 12 shifts · 2024: 0 in 18 shifts · 2025: 0 in 8 shifts · 2026: 0 in 9 shifts.

Shift by shift

Each square is one analysed shift, in date order. Open a filled one for that paper.

  • 20260 of 9
  • 20250 of 8
  • 20240 of 18
  • 20230 of 12
  • 202224 of 24
  • 20212 of 24
  • 20200 of 12
  • 20170 of 1

Asked in that shift More than once Not asked

How JEE Main framed it

Single correct is the usual form. Skill tested: calculation.

  • Time for fractional decay
  • Half-life from fraction decayed

Difficulty

Easy 5Medium 2Hard 0

3 of the 7 questions had a numerical answer.

Every question

All 7 questions

From the official JEE Main shift papers, newest first. Open one for the full question, the options and the official answer.

  1. 24 Jun 2022, Shift 2 · Q56A sample contains 10−210^{-2} kg each of two substances A and B with half lives 4 s and 8 s respectively. The ratio of their atomic weights…MediumNumerical value
  2. 28 Jul 2022, Shift 2 · Q18A radioactive sample decays 78\frac{7}{8} times its original quantity in 15 minutes. The half-life of the sample isEasySingle correct
  3. 28 Jul 2022, Shift 1 · Q48The half life period of a radioactive substance is 60 days. The time taken for 78\frac{7}{8}th of its original mass to disintegrate will…EasySingle correct
  4. 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
  5. 27 Jul 2022, Shift 1 · Q48What is the half-life period of a radioactive material if its activity drops to 1/16th^{th} of its initial value in 30 years?EasySingle correct
  6. 25 Jul 2021, Shift 2 · Q27The nuclear activity of a radioactive element becomes (18)th\left(\frac{1}{8}\right)^{\text{th}} of its initial value in 30 years. The…EasyNumerical value
  7. 25 Feb 2021, Shift 1 · Q19Two radioactive substances X and Y originally have N1N_1 and N2N_2 nuclei respectively. Half life of X is half of the half life of Y.…MediumSingle correct

Shifts: 25 Feb 2021, Shift 1, 25 Jul 2021, Shift 2, 24 Jun 2022, Shift 2, 27 Jul 2022, Shift 1, 28 Jul 2022, Shift 2, 28 Jul 2022, Shift 1.

Same topic

Other ideas in Radioactive Decay

Radioactive Decay has 12 ideas JEE Main has asked; 9 of them came up in more than one question.

Topic analysisChapter analysisStudy this chapterAll repeated ideas