Abstract
This paper discusses the difficulties in interpreting the absorption spectra of a particular monoatomic gas filled in a chamber with perfectly reflective inner walls. If those gas atoms absorb photons of frequency ν from white light falling on them, how they can continue to absorb them cannot be explained on the lines of conservation of energy, which is always overlooked. This paper traces that there is something else here that is not yet understood. One thing that to understand is that if an atom produces a light wave of frequency ν, the electron that generated this wave due to its transition must oscillate at one place in the atom with that frequency which can be the natural frequency of that electron at that place. But no atomic model is in a position to support this. When a light wave of the same frequency interacts with the same electron of the atom, it should oscillate at the same frequency in resonance. But if there is a difference of 180 degrees between the light wave created by the oscillations of that electron and the light wave interacting that electron, no net wave can be created or come out, so a black line will appear at the frequency ν at absorption spectrum of gas of such atoms. No matter how long light is shone on that gas, this condition will remain forever.