Activity is the measure of the number of radioactive decays per unit time in a given sample. It is typically measured in becquerels (Bq) or curies (Ci).
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The SI unit for activity is the becquerel (Bq), which corresponds to one decay per second.
Activity decreases over time as a result of radioactive decay, following an exponential decay law.
It can be calculated using the equation $A = \lambda N$, where $A$ is the activity, $\lambda$ is the decay constant, and $N$ is the number of undecayed nuclei.
The relationship between half-life ($T_{1/2}$) and decay constant ($\lambda$) is given by $\lambda = \frac{0.693}{T_{1/2}}$.
Knowing the activity helps in determining the safety and usage of radioactive materials in practical applications.
Review Questions
What is the SI unit for measuring activity?
How does activity change over time for a radioactive substance?
Write down the formula that relates activity ($A$), decay constant ($\lambda$), and number of undecayed nuclei ($N$).
Related terms
Half-Life: The time required for half of the radioactive nuclei in a sample to undergo decay.
Decay Constant: A parameter that represents the probability per unit time that a nucleus will decay.
Becquerel: The SI unit of radioactivity, defined as one disintegration per second.