When struck by a photon, 11-cis retinal undergoes photoisomerization to all-trans retinal which changes the conformation of the opsin GPCR leading to signal transduction cascades which causes closure of cyclic GMP-gated cation channel, and hyperpolarization of the photoreceptor cell.
From the physics point of view, does this mean the proteins in the eye are combinations of oscillators, each of them in charge for a specific wavelength, so that if one oscillator resonates with the photon, the signal is produced? In general, does all receptors work this way? Note that physical oscillators should have exponential or sinusoid functions. See this Photography question: How to capture a swinging pendulum?