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Saturday, 31 October

JEE Main · Physics · Nuclei

Half-Life Calculations

JEE Main asked Half-Life Calculations 10 times in 9 of the 108 shifts Lumi analysed, in 2020, 2021, 2022 and 2023. It belongs to Radioactive Decay, in Nuclei (Physics). The longest wait between two years asking it was 1 year. In 2021, 2022 and 2023 it came in more than one shift of the same year.

Updated 2026-10-24

Times asked
10
in 9 shifts
Years
4 of 8
First asked
2020
last in 2023
Pattern
Comes in cycles
across the analysed shifts

Questions on this idea a shift, by year

2017–2026. Asked in 2020, 2021, 2022 and 2023. Years differ in how many shifts Lumi analysed, so each year is scaled to one shift of 25 Physics questions.

00.150.30’170.08’200.14’210.07’220.21’230’240’250’26

Raw count: 2017: 0 in 1 shift · 2020: 1 in 12 shifts · 2021: 4 in 24 shifts · 2022: 2 in 24 shifts · 2023: 3 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
  • 20233 of 12
  • 20222 of 24
  • 202123 of 24
  • 20201 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 interval between fractional decays
  • Time for fractional decay of activity

Difficulty

Easy 8Medium 2Hard 0

1 of the 10 questions had a numerical answer.

Every question

All 10 questions

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

  1. 15 Apr 2023, Shift 1 · Q44The half-life of a radioactive nucleus is 5 years. The fraction of the original sample that would decay in 15 years is:EasySingle correct
  2. 10 Apr 2023, Shift 2 · Q44The half life of a radioactive substance is T. The time taken, for disintegrating 78\frac{7}{8}th part of its original mass will be:EasySingle correct
  3. 8 Apr 2023, Shift 2 · Q44A radio active material is reduced to 1/8 of its original amount in 3 days. If 8×10−38\times10^{-3} kg of the material is left after 5 days…MediumSingle correct
  4. 29 Jun 2022, Shift 1 · Q33The activity of a radioactive material is 2.56×10−32.56 \times 10^{-3} Ci. If the half life of the material is 5 days, after how many days the…EasySingle correct
  5. 27 Jul 2022, Shift 2 · Q48The activity of a radioactive material is 6.4×10−46.4\times10^{-4} curie. Its half life is 5 days. The activity will become 5×10−65\times10^{-6}…EasySingle correct
  6. 16 Mar 2021, Shift 2 · Q10Calculate the time interval between 33% decay and 67% decay if half-life of a substance is 20 minutes.EasySingle correct
  7. 27 Aug 2021, Shift 1 · Q19There are 101010^{10} radioactive nuclei in a given radioactive element. Its half-life time is 1 minute. How many nuclei will remain after…EasySingle correct
  8. 3 Aug 2021, Shift 2 · Q18A radioactive isotope has a half life of T years. After how much time is its activity reduced to 6.25% of its original activity ?EasySingle correct
  9. 3 Aug 2021, Shift 2 · Q25A sample undergoing beta decay, reduced to 116th\frac{1}{16}^{\mathrm{th}} of its initial mass in 48 years. Its half life period is…EasyNumerical value
  10. 5 Sep 2020, Shift 1 · Q18Activities of three radioactive substances A, B and C are represented by the curves A, B and C, in the figure. Then their half-lives…MediumDiagram basedHas a figure

Shifts: 5 Sep 2020, Shift 1, 16 Mar 2021, Shift 2, 3 Aug 2021, Shift 2, 27 Aug 2021, Shift 1, 29 Jun 2022, Shift 1, 27 Jul 2022, Shift 2, 8 Apr 2023, Shift 2, 10 Apr 2023, Shift 2, 15 Apr 2023, 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