= Principle of univariance
{title2=$Q=\int N(\lambda)a(\lambda)\,d\lambda$}
A receptor's absorption-dependent response does not independently label the <wavelength> of an absorbed <photon>. Different combinations of spectral composition and <intensity> can yield the same <receptor quantum catch>. Comparing spectrally distinct receptor classes can supply information unavailable from one alone. In the displayed model, $N$ is a <photon> distribution and $a$ effective absorptance; an energy spectrum would require the corresponding photon-energy conversion.
Back to article page
