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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceSingle correctEasyApplication

JEE Main 16 March 2021, Shift 2, Physics Q10

Question 10 of 90 in this shift, Physics question 10 of 30, Section A.

Calculate the time interval between 33% decay and 67% decay if half-life of a substance is 20 minutes.
  1. (1)20 minutesOfficial answer
  2. (2)40 minutes
  3. (3)60 minutes
  4. (4)13 minutes

Official answer

Option 1

NTA final key.

Chapter
Nuclei
Topic
Radioactive Decay
Idea tested
Half-Life Calculations

Same idea in other shifts

Asked 10× in all
  1. 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
  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. 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
  4. 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
  5. 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
  6. 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
  7. 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
  8. 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

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.