Find the wavelength in nanometers of a photon emitted by a hydrogen atom decaying from the 3s state to the 2s state.

Answer 1

delta E = 2.18E-18 J(1/2^2 - 1/3^2), then
dE = hc/w. h is Planck's constant. c is speed of light in m/s. w is wavelength in m. Convert to nm. Post your work if you get stuck.

Answer 2

Thank you! It makes sense now.