Which statement correctly relates curie and becquerel?

• A. 1 curie equals 3.7 × 10^10 decays per second; 1 becquerel equals 1 decay per second
• B. 1 curie equals 3.7 × 10^8 decays per second; 1 becquerel equals 100 decays per second
• C. 1 curie equals 3.7 × 10^12 decays per second; 1 becquerel equals 1 decay per second
• D. 1 curie equals 1 decay per second; 1 becquerel equals 3.7 × 10^10 decays per second

Answer: (A)

The key idea is the relationship between an older large-unit and the SI unit for activity. The becquerel is defined as 1 disintegration per second, while the curie is defined as 3.7 × 10^10 disintegrations per second. Therefore, a curie corresponds to a fixed, much larger rate of decay: 1 Ci = 3.7 × 10^10 Bq, and 1 Bq = 1 dps. That makes the statement describing both values correct. In practice, you can convert by multiplying by 3.7 × 10^10 to go from curies to becquerels, or by dividing by 3.7 × 10^−10 to go the other way.