>In such a case, it is possible to determine both the amplitude and the frequency of any electromagnetic radiation, e.g. light, with a frequency intermediate be

>In such a case, it is possible to determine both the amplitude and the frequency of any electromagnetic radiation, e.g. light, with a frequency intermediate between the 2 peak frequencies of the receptors, from the 2 values provided by the 2 receptors. Is it? How would you distinguish between monospectral illumination at a frequency between the two peaks and lower amplitude polyspectral illumination at each of the peaks? That ambiguity is essentially the basis of rgb displays.