Isotope P is radioactive, and its half-life is $7.0$ years. Initially, a sample has $0.016\,\text{kg}$ of P. How long will it take before the sample has $0.0020\,\text{kg}$ of P?
- A$7.0$ years
- B$14$ years
- C$21$ years
- D$28$ years
Physics 5054 · O Level · Half-life