A radioactive isotope has a half-life of 1386 s. What is its decay constant (λ = 0.693/T½)?
Correct answer C. 5.0 × 10⁻⁴ s⁻¹
Explanation
λ = 0.693/T½ = 0.693/1386 = 5.0 × 10⁻⁴ s⁻¹. Using 1/T½ without 0.693 gives the wrong value 7.2 × 10⁻⁴ s⁻¹.
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