In a given sample, at some instant, the rate of disintegration of a radioactive element is 8000 disintegrations per second. At this instant, the number of undisintegrated nuclei of this element is 8*10⁷. Find the decay constant and half-life of this element. [Ans: λ=10⁻⁴ s⁻¹, τ^1/2= 6390 s]