Answer
In an exponential decay model,
the time needed for the substance to decay to half of its initial quantity.
Work Step by Step
Half-time is related to the
Exponential decay model: $A=A_{0}e^{kt} \quad (k<0)$
(where $A_{0}$ is the initial quantity, and $A$ is the quantity after time t)
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At some point of time, the quantity $A$ will become half the initial quantity, $A_{0}$.
(The initial quantity decays to half)
The time needed for this to happen is the half-life of the substance.
It is calculated by solving
$0.5A_0=A_{0}e^{kt}$
for t
