Got it ! ! What a miracle . <| sep |> Where are the aliens ? <| sep |> The problem is that with a distribution , you can ' t plot the intensity at a specific wavelength or intensity , because that ' s actually zero . You ' re really plotting how the total intensity changes with intensity or frequency . You ' re not plotting If for instance , you ' re plotting dIdf , and the peak of that will change if you change the ddf with another variable . More intuitively , thinking of it as binning things in a histogram , with equal sized intervals . By wavelength , you put all the energy from 100200 nm in one bin , all the energy from 200300 nm in the next bin , 300400 nm in the next bin , and so on . But those bins don ' t have equal size in frequency those same bins are 3000 THz 1500 THz , then 15001000 THz , then 1000750 THz . And if you use equal sized bins of frequency , you ' re actually binning over different sized bins of wavelength . So you ' re really looking at different ranges depending on what units you use , and you will find different peaks .