Question 47
Radioactivity and Nuclear PhysicsA piece of radioactive material contains 1000 atoms. If its half-life is 20 seconds, the time taken for 125 atoms to remain is
- A.20 seconds
- B.40 seconds
- C.60 seconds
- D.80 seconds.
Show the answer and explanation
Answer: C (60 seconds)
Explanation
1000 → 500 → 250 → 125 is three half-lives: 3 × 20 = 60 s.