[kridsdale1]

I suppose my interpretation of his message is that if you think of a “ray of light” that is not a mono frequency laser as an “input signal”, a convex lens will smear it out in to its constituent component frequencies. From that perspective you can analyze the original signal (aka color) with a geometrically/spatially separated spectrum of values.

It was a single spatial point of ray intersection with your sensor or eye. You’d need color filters/retinal cells to pick apart the frequencies in the complex waveform.

After rainbow separation, the components are spread across multiple sensors giving you a frequency domain view.