The Radioactive Decay Calculator computes the remaining quantity of a radioactive substance using the exponential decay formula N=N0e−λtN = N_0 e^{-\lambda t}N=N0​e−λt, where λ=ln⁡2/T1/2\lambda = \ln 2 / T_{1/2}λ=ln2/T1/2​ is the decay constant. By entering the half-life and any two of the remaining variables (initial quantity, remaining quantity, or elapsed time), the calculator determines the unknown. This tool is useful for physics, nuclear science, and radiometric dating calculations.

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