[xtheunknown0]

As I understand, different elements have different emission spectra because the light they emit is a mixture of different colours. If all forms of spectroscopy use a part of the electromagnetic spectrum, why isn't the yellow of the emission spectrum of cadmium in exactly the same position as the yellow of the emission spectra of sodium?

TIA,
xtheunknown0

[Borek]

There is more than one wavelength that we see as yellow.

[chronictonic]

So the cadmium atoms and the sodium atoms both absorb light. and as they do their electrons jump up to a higher energy level. when the drop back down they emit a photon of light, in this instance yellow (or a very specific wavelength of what we see as 'yellow'). The thing that determines the wavelength is the difference between the two energy levels. I am not certain of the specific energies of the transitions in sodium and cadmium but the reason is because the difference of the two transition state's energy levels are equal. I would suspect that cadmium has a few lines of emission, one of them happens to correspond with the same energy gap as sodium. remember that atoms energy levels are quantized and so many different atoms may have common emission lines in the spectrum.