Question

define decay constant​

Answer 1

The decay constant is the fraction of the number of atoms that decay in 1 second. It is the constant λ in thedecay equation: dN/dt = -λN The - sign indicates decay, dN/dt is the number of decays per second (also known as 'Activity') and N is the number of atoms present.

Answer 2

The decay constant is the probability of atoms decaying in a unit time. It is denoted by λ. It can be denoted mathematically as:

dNNdt=−λ

Its unit is s−1, the same units as that of frequency. Probability has no units, so the only units in the mathematical expression is that of time, which in the denominator is seconds s.

Here, dNN represents the probability of atoms decaying and dt represents the interval of time being considered. The R.H.S term is negative because the process involved here is radioactive decay, so the rate is the rate of decrease of the no. of undecayed atoms, and the rate of decrease is negative.

Rearranging the equation,

dNdt=−λN