I don't know a whole lot about quantum mechanics and there is something that dosen't make sense to me. An atom absorbes radiation in only certin frequencies. Do these frequencies have to be exact? Can they vary over a small range like say 1.000 to 1.001 or do they have to be perfectly exact? If they are exact then it would seem to me that if radiation which continuously ranged over many frequencies was exposed on atoms, the atoms would absorb none of it. But this is not the case because the sun emits radiation which continuously ranges over many frequencies (right?) and gaps are observed in the spectrum where certin atoms absorbe it. So where am I wrong?