For a radioactive isotope obeying first-order kinetics, what fraction of the original sample remains undecayed after 4 half-lives?

Answer and explanation

Correct answer: D.

  1. Step 1: In first-order radioactive decay, the fraction of nuclei remaining after half-lives is .
  2. Step 2: Given half-lives.
  3. Step 3: Compute: .
Answer
.
Why not the others: corresponds to 3 half-lives; corresponds to 5 half-lives; corresponds to 6 half-lives.

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