試題詳解

60. The radioactive isotope  ²²⁶Ra decays to ²²² Rn with a half-life of 1600 years. The radioactive isotope  ²³⁸U decays to²³⁴ Th  with a half-life of 4.5× 10⁹ years. What is the ratio of the decay rate of 1 g  ²²⁶Ra to that of 10 g²³⁸ U  ?
(A) 3.0 × 10⁶
(B) 3.0 × 10^-7
(C) 3.0 × 10⁵
(D) 3.0 × 10^-6
(E) 3.0 × 10⁷