Modern Physics
Radioactive Decay Law
The number of radioactive nuclei decreases exponentially with time.
Variables
N(t)unitless
Number of nuclei at time t
Allowed values: greater than 0
N0unitless
Initial number of nuclei
Allowed values: greater than 0
λs⁻¹
Decay constant
Allowed values: greater than 0
ts
Time
Allowed values: 0 or more
Your notes
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Check value
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- N0 = 2 (Initial number of nuclei)
- λ = 3 s⁻¹ (Decay constant)
- t = 4 s (Time)
Result: N(t) = 1.228842 × 10⁻⁵
Where this formula is listed
- Modern Physics formulas, under Nuclear Physics, alongside Nuclear Binding Energy, Alpha Decay Energy (Q-value), Beta Decay and Nuclear Radius.
- In the modern physics list it comes after Moseley's Law and before Half-Life.
- Modern Physics formula sheet, one of 41 formulas printed with symbol keys and SI units.
- The full formula index, grouped by category and topic.
Common questions
What is the Radioactive Decay Law formula?
Radioactive Decay Law is written N(t) = N₀e^(−λt). The number of radioactive nuclei decreases exponentially with time. It belongs to Modern Physics, under Nuclear Physics.
What are the units in N(t) = N₀e^(−λt)?
In SI units, N(t) is number of nuclei at time t (dimensionless); N₀ is initial number of nuclei (dimensionless); λ is decay constant, measured in s⁻¹; t is time, measured in s.