# What does the term $e^{-h\nu /kT}$ in Boltzmann distribution function mean and what roles does it play? [duplicate]

What is the physical meaning of $$e^{-h\nu /kT}$$ in the Boltzmann distribution function. I am aware that $$h\nu$$ represents energy of a photon and $$kT$$ is the thermal energy available to the system. I know $$-h\nu /kT$$ is the ratio between the 2 energies, but I'm not sure what it represents in general and why $$h\nu$$ is included. Thanks for helping out.

## marked as duplicate by caverac, LonelyProf, By Symmetry, Buzz, Jon CusterDec 16 '18 at 3:42

The physical idea that comes to my mind is that the Boltzmann factor $$e^{\frac{-h\nu}{kT}}$$ expresses the probability of finding a state with energy $$E = h\nu$$ relative to the probability of finding a state with energy zero.