<i>&gt; You&#x27;re badly mistaken.</i><p>No, I&#x27;m not; you&#x27;re just mistaken about which classical results I was referring to. I meant the results of classical EM that predicted that atoms could not exist--because the electrons would radiate until they fell into the nucleus. And what classical formula tells you how much the electrons will radiate because of their acceleration due to responding to the electric field of the nucleus? Larmor&#x27;s formula.<p>In other words, Larmor&#x27;s formula was not a &quot;theory&quot;--it was a particular result derived within a theory. The particular <i>result</i> happened to be correct, within a particular limited domain; but the underlying <i>theory</i> that was used to derive it could not explain <i>why</i> it was correct--because the same theory, and indeed the same particular result--the same formula--made other predictions that were obviously egregiously wrong (like predicting that atoms would collapse).<p><i>&gt; nobody succeeded in obtaining the emission line frequencies of gases out of the classical EM theory</i><p>You&#x27;re drastically understating the failure of classical EM here. It&#x27;s not that classical EM couldn&#x27;t predict the particular frequencies of emission lines. It&#x27;s that classical EM couldn&#x27;t predict the <i>existence</i> of emission lines at all. Classical EM predicted that atoms would emit a continuous spectrum of radiation--not radiation sharply peaked at particular frequencies.<p><i>&gt; The classical formula is taught to this day both in macroscopic EM theory and quantum optics courses</i><p>Sure, because <i>within its domain of validity</i>, it works fine as an approximation. But that&#x27;s all it is--an approximation. And we explain why the approximation works, and why it works only within a particular domain of validity, by reference to the more complete underlying theory--quantum electrodynamics.<p><i>&gt; I do not know what you mean by &quot;correct&quot;.</i><p>I mean &quot;makes predictions that match the results of experiments&quot;.