is the wavelength equal to the distance between the excited state shell and the rest state shell?
Could you please give more context. Are you talking about atoms?
In fact, that statement is totally the wrong way round . The bigger the spacing between the shells (not a good way of looking at it, really because it's the energy difference that counts, rather than the hand-waving idea of spacing) the shorter the wavelength. This is because the frequency associated with the emitted is proportional to the energy change in the atom.
yes, i was talking about atoms but i guess the answer is no.
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