Radioactive decay is a random and spontaneous process it depends on unbalancing of nucleus.
N = N0e–λt …(B)
ln N = –λt + lnN0
So, slope = – λ …(C)
t1/2=\(\frac{ln2}{lλ}\)
So t1/2 × λ = ln2 = Constant
The half-life of a radioactive nucleus is 5 years. The fraction of the original sample that would decay in 15 years is:

The amount of time taken for half of a particular sample to react is known as Half-life.
We can describe exponential decay by any of the three formulas

