# Hydrogen Emission vs Absorption Wavenumbers

I am used to using the formula $$R_H (\frac{1}{n^2_{final}}-\frac{1}{n^2_{initial}})$$ to calculate the transition wavenumbers when an electron in a Hydrogen atom emits a photon. Can you use the same formula to calculate the wavenumber when a electron absorbs a photon?

• Do you mean emit/absorb an electron? If so, your question is easily answered: take $$1/n_{initial) = 0 and n_{final}$$ to be whatever PQN the electron was absorbed into. Jul 27, 2020 at 11:32
• @AravindSuresh no sorry I made a mistake, I mean when the electron absorbs/emits a photon, I suppose it doesn't matter if it's in Hydrogen apart from I've used the Rydberg constant for hydrogen. Jul 27, 2020 at 11:42

• You'd have to rearrange it, Maybe it's easier to visualize if you think of this equations in terms of energy rather than wavelengths: if you multiply both sides of the Rydberg equations by $hc$ you obtain $\Delta E = hcR_H (1/n_1^2-1/n_2^2)$. $\Delta E$ is the difference in energy between both levels, and its sign indicates if the transition requires or releases energy. Jul 27, 2020 at 21:37