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Calculate the decay constant of a radioactive isotope of half-life 138.5 s.

Physics
JAMB 2025

Calculate the decay constant of a radioactive isotope of half-life 138.5 s.

  • A. 5.0 × 10\(^{-3}\) s\(^{-1}\)
  • B. 5.1 × 10\(^{-3}\) s\(^{-1}\)
  • C. 4.9 × 10\(^{-3}\) s\(^{-1}\)
  • D. 5.2 × 10\(^{-3}\) s\(^{-1}\)
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Correct Answer: Option A
Explanation

Answer: A

λ = \(\frac{ln2}{T½ }\) ⇒ \(\frac{0.693}{138.5}\)  ≈ 5.0 × 10\(^{-3}\) s\(^{-1}\).

There is an explanation video available below.

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Explanation Video

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