How is color vision determined?

Color vision is fundamentally determined by the relative responses of different types of photoreceptors present in the retina, specifically the cones that are sensitive to varying wavelengths of light. Humans typically have three types of cones—S-cones (short wavelength sensitive), M-cones (middle wavelength sensitive), and L-cones (long wavelength sensitive). Each type of cone responds to a different range of wavelengths.

When light hits the photoreceptors, it triggers a photochemical response that produces a signal proportional to the intensity of the light at specific wavelengths. The brain interprets color by comparing the signals from these three types of cones. Thus, color perception arises from the pattern of stimulation across the cone types rather than the absolute number of photons absorbed by any single one.

This relative comparison enables the brain to distinguish a wide spectrum of colors, as it evaluates the balance of responses from the different cone types. Therefore, the answer that states color vision is determined by the relative responses of photoreceptors based on the number of photons absorbed is accurate, reflecting how the visual system encodes color information through differential activation of these photoreceptors.