A diagram, essentially a graph in the form of a right-angled isosceles triangle of consequent dimensions, 1 ,1, sqrt2 is developed and which represents, in dimensionless form, the individual spectrums of electromagnetic radiation in all media of constant index of refraction. Initially, the metric coordinates associated with the construction are rendered dimensionless by employing the Planck frequency, (V), and Planck length, (L), regarded as a wavelength, as scaling factors. Hence, for the diagram shown here the dimensioned spectrums lie in the ranges, 0 to (V) and infinity to (L).

Further, it is shown that the diagram is universal, in that , other diagrams, covering different ranges, but with identical shape may be constructed provided that the product of the scaling factors of frequency and wavelength is equal to the speed of light in vacuo.