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Friday, 9 October

JEE Main 2022 · PhysicsMultiple choiceSingle correctEasyCalculation

JEE Main 28 July 2022, Shift 1, Physics Q48

Question 48 of 90 in this shift, Physics question 18 of 30, Section A.

The 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 be :
  1. (1)120 days
  2. (2)130 days
  3. (3)180 daysOfficial answer
  4. (4)20 days

Official answer

Option 3

NTA final key (2022 Session 2).

Chapter
Nuclei
Topic
Radioactive Decay
Idea tested
Integer Half-Life Shortcuts

Same idea in other shifts

Asked 2× in all
  1. 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

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.