1.Intensity is directly proportional to energy.
2.Energy is directly proportional to frequency or inversely proportional to wavelength.
3.From 1 and 2 it is evident that INTENSITY and WAVELENGTH are inversely proportional.
But note that these statements are valid in case of a single photon.
In the above query this principle is not applicable as instead of a single photon we are provided the H spectrum to work with.Here instead of relation between intensity and wavelength,we use the relation between intensity and amplitude which I guess is experimentally found in different spectrums .As of now I hope it is better to learn what is given in the text as it is..coz when it comes to spectrums I don't think that there is a direct relation between these 2 quantities.