Position of the Signal:

You know that in spectroscopy, we have to study about the interaction of radiation and matter. This interaction is manifested within terms of absorption, emission or scattering of the radiation. In that case of atomic species, an interaction causes transitions amongst the electronic energy levels. While, you have learnt which in case of molecules, an interaction led to transitions amongst the rotational, vibrational or electronic energy levels or combinations of these. Therefore, like in case of molecular spectra, here also the position of the spectral signals is determined by the difference in the energies of different energy levels. If E₂ and E₁ represent the energy of the higher and lower energy levels concerned, the energy modifies during the transition from E₂ to E₁ level may be defined as follows.

ΔE = (E₂ - E₁) =  hv  =  hc/λ

Or       λ = hc/(E₂  - E₁) = hc/ΔE

here, h is the Planck's constant, c is the velocity of light, v the frequency and λ the wavelength of the emitted radiation. The wavelength of the radiation is features of the atoms of the particular element from that it are emitted. While flame photometry is employed as an analytical tool, a wavelength of the radiation emerging from a flame tells us about the elements which are present in that flame.