Nuclear measurements: the radioactivity (decay rate) of an isotope is commonly expressed in which unit?
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Abarn
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BMeV
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CCurie
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Derg
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EBecquerel
Answer
Correct Answer: Curie
Explanation
Introduction / Context:Radioactivity quantifies the number of nuclear disintegrations per unit time. Historically and in many references, the Curie (Ci) is used, while the SI unit is the Becquerel (Bq).
Given Data / Assumptions:
- We are asked for the commonly used unit for activity (decays per second).
- Options include units for cross-section, energy, and activity.
Concept / Approach:The Curie is defined as 3.7 × 10^10 disintegrations per second, originally based on the activity of 1 gram of radium-226. The SI unit Becquerel equals 1 disintegration per second. A barn measures nuclear reaction cross-sections; MeV and erg are energy units.
Step-by-Step Solution:
1) Identify the property: activity = decay rate.2) Match activity to unit: Curie (traditional) and Becquerel (SI).3) From the listed options, Curie is the correct match.Verification / Alternative check:Dimensional analysis and definitions confirm that Bq and Ci measure events per time, whereas barns and MeV/erg do not.
Why Other Options Are Wrong:
- Barn: area unit for cross-sections.
- MeV/erg: energy units.
- Becquerel: correct SI unit, but the specific correct choice here is Curie as per the option list focus.
Common Pitfalls:Confusing cross-section (barn) or energy (MeV) with activity.
Final Answer: Curie