1. The problem statement, all variables and given/known data Question 1) For absorption transitions: At n=1 the energy is 0.0eV (electron volts), at n=2 the energy is 3eV, at n=3=5eV Question 2) For emission transisions: At n=1 the energy is 0.0eV, n=2 energy is 3eV and at n=3 energy is 5eV Question 3) The atom has energy levels n=1(0eV),n=2(2eV) and n=3(5eV). A photon has energy E=3eV which corresponds to spectral line with λ=414nm. Where would this spectral line be observed? absorption spectrum, emission spectrum, both or neither? 2. Relevant equations ΔE between the energy levels for an absorption transition ΔE= E1 - E2 etc.. ΔE between the energy levels for an emission transition ΔE=E3 - E2 etc.. λ=c*h/ΔE 3. The attempt at a solution Question 1) So to find the difference in energy ΔE between the energy levels for an absorption transition at ΔE=E1 - E2, then ΔE= 0.0eV - 3eV = -3eV but in my notes this answer is positive 3eV what am i doing wrong? Question 2) To find emission transition at ΔE=E3 - E2 , then ΔE= 5eV-3eV= 2eV but in my lecture notes the answer given is negative -2eV i do not see how this is possible and where i went wrong? Question 3) Since E=3eV, I would assume it would be an emission spectrum because ΔE=E3 - E2=3eV but shouldn't the 3eV be negative because for an emission transion ΔE=E3 - E2 in question 2 the answer given was negative.