What is the Decay constant?

The decay constant is defined as the ratio of amount of substance decayed per unit time to amount of substance present at that time.

we know ,

N = N₀ e^-λt

and t = 1 /λ

Substitute t= 1 /λ in above formula we get

N = N₀ e^-λ(1/λ)

N = N₀ e^-1

N = N₀ / e

N = N₀ /2.718

N = 0.37 N₀

Now decay constant can also be defined as the reciprocal of the duration in which a substance decays at 37% of its original quantity.