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JEE Main 2023 · 29 Jan · Shift 1

JEE Main 2023 Physics question on Atoms and Nuclei

If a radioactive element having half-life of 30 min is undergoing beta decay, the fraction of radioactive element remains undecayed after 90 min. will be
  1. A.
    14\frac{1}{4}
  2. B.
    116\frac{1}{16}
  3. C.
    12\frac{1}{2}
  4. D.
    18\frac{1}{8}
Show answer and solution

Correct option: D

Solution

90 min = 3 half-lives (since 90/30 = 3). After n half-lives, the remaining fraction is (1/2)n = (1/2)³ = 1/8.

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