Question 47
Radioactivity and Nuclear PhysicsA piece of radioactive material contains 1020 atoms. If the half-life of the material is 20 seconds, the number of disintegrations in the first second is
- A.3.47 × 1018.
- B.6.93 × 1020.
- C.3.47 × 1020.
- D.6.93 × 1018.
Show the answer and explanation
Answer: A (3.47 × 1018.)
Explanation
Decay constant λ = 0.693 ÷ 20 = 0.0347 s−1. Activity = λN = 0.0347 × 1020 = 3.47 × 1018 per second.