1. The problem statement, all variables and given/known data There is an electronic transition between the first energy state and the ground state of a neon atom, emitting a wavelength of 746nm. The question asks for the energy of the transition and an estimate of the fraction of atoms in a sample that is thermally excited at 300K. 2. Relevant equations My guess: E = hc/λ. P(E) ∝ √E⋅e-E/kT 3. The attempt at a solution So surely finding the energy is easy: E = hc/λ = (6.63x10-34)(3x108)/(746x10-9) = 2.666x10-19 J ≈ 2.7x10-19 J However, I have a feeling this is too simple and might be incorrect. For the probability, I suppose you use the Boltzmann Distributuon: P(E) ∝ √E⋅e-E/kT ∴P(E) ∝ 6.43x10-38 But this is probably just the probability of getting exactly the energy value above - what I really want (I think) is the probability of the energy being equal to or greater than the energy value calculated above, i.e. the probability of E ≥ 2.7x10-19 J Can someone point me in the right direction, and tell me where I might have gone wrong? Thanks.