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What is activity, R, as used to describe a radioactive sample?
AThe rate of decay, expressed in decays per unit time
BThe total number of atoms remaining in the sample
CThe energy released by a single decay event
DThe temperature of the radioactive material
Answer & Solution
Correct answer: A. The rate of decay, expressed in decays per unit time
1. Activity describes how many decays happen in a sample, not simply how many atoms remain.
2. It is defined as the rate of decay, expressed in decays per unit time.
3. It is not the energy of a single event, and it is not the material's temperature.
4. So the rate of decay per unit time is correct.
_Source: OpenStax Physics (CC BY 4.0), Ch 22 "The Atom", section 22.3 Half Life and Radiometric Dating_
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