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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceSingle correctEasyApplication

JEE Main 4 August 2021, Shift 1, Physics Q4

Question 4 of 90 in this shift, Physics question 4 of 30, Section A.

A hypothetical radioactive nuclei decays according to the following series 72180A→αA1→β−A2→αA3→γA4^{180}_{72}A \xrightarrow{\alpha} A_1 \xrightarrow{\beta^-} A_2 \xrightarrow{\alpha} A_3 \xrightarrow{\gamma} A_4 The atomic number and mass number of A4A_4 will be respectively
  1. (1)69, 172Official answer
  2. (2)69, 171
  3. (3)70, 172
  4. (4)68, 171

Official answer

Option 1

NTA final key.

Chapter
Nuclei
Topic
Radioactive Decay
Idea tested
Counting Alpha and Beta Emissions

Same idea in other shifts

Asked 3× in all
  1. 26 Jun 2022, Shift 1 · Q48How many alpha and beta particles are emitted when Uranium 92U238_{92}\mathrm{U}^{238} decays to lead 82Pb206_{82}\mathrm{Pb}^{206} ?EasySingle correct
  2. 29 Jun 2022, Shift 2 · Q35In the following nuclear reaction,…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.