Concepts Of Physics MCQ Edition [Volume 2]PhysicsThe Nucleus
Given that the decay constant of ²³⁸ U is 4.9 10⁻¹⁸ s ⁻¹ , find the half-life of ²³⁸ U .
Options
- A2.25 10⁹ y
- B6.5 10⁹ y
- C9.0 10⁹ y
- D4.5 10⁹ y
Correct answer
D. 4.5 10⁹ y
Step-by-step solution
The half-life of a radioactive substance is given by: T_ 1/2 = 2 = 0.693 Substituting = 4.9 10⁻¹⁸ s ⁻¹ : T_ 1/2 = 0.693 4.9 10⁻¹⁸ s = 1.414 10¹⁷ s Converting the half-life from seconds to years ( 1 year 3.154 10^7 s ): T_ 1/2 = 1.414 10¹⁷ 3.154 10^7 y T_ 1/2 4.48 10^9 y 4.5 10^9 y