Radioactive Decay Rate Calculator
Calculate Activity (A)
A = λN (decays per second)
Specific Activity
Activity per gram of radioactive isotope
Remaining Activity After Time
Formula
A = λN | λ = ln(2)/t½ | A(t) = A₀ × (1/2)^(t/t½) | SA = λNₐ/M | 1 Ci = 3.7 × 10¹⁰ Bq
Frequently Asked Questions
What is radioactive decay rate (activity)?
Activity (A) is the number of nuclear disintegrations per unit time. A = λN, where λ is the decay constant and N is the number of radioactive atoms. Units: Becquerel (Bq) = 1 decay/s, Curie (Ci) = 3.7 × 10¹⁰ decays/s.
What is specific activity?
Specific activity is the activity per unit mass of a radioactive isotope: SA = λNₐ/M (Bq/g). Shorter half-lives give higher specific activity. For example, I-131 (t½=8d) has much higher specific activity than U-238 (t½=4.5×10⁹ yr).
How does activity change over time?
Activity decays exponentially: A(t) = A₀ × (1/2)^(t/t½) = A₀ × e^(-λt). After one half-life, activity halves. After 10 half-lives, ~0.1% remains. Activity is directly proportional to the number of remaining atoms.
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