Which wavelengths have the best wavelength discrimination in a normal trichromat?

In normal trichromatic vision, wavelength discrimination is best in the region where the three types of cone photoreceptors (S-cones, M-cones, and L-cones) are most responsive to different parts of the light spectrum. The most effective discrimination occurs in the area where the spectral response curves of these cones overlap, allowing for better differentiation of colors.

The correct selection of 495 nm and 555 nm represents wavelengths that are well within the sensitivity range of the cones. At 495 nm, which corresponds closely to the peak sensitivity of M-cones, there is strong overlap with L-cone sensitivity. Similarly, 555 nm is close to the peak response of L-cones. This overlap enhances the ability to discriminate between the stimuli of these wavelengths, as the corresponding cones are stimulated effectively, allowing for fine differentiation of colors.

In contrast, the other options mix wavelengths where discrimination may be less optimal due to lower sensory responses from at least one type of cone. For example, wavelengths around 475 nm and 590 nm may involve significant differences in responses between the cones, reducing the ability to discriminate between them effectively. Thus, the best discrimination comes from the combination found in the selected pair, where the cone responses provide optimal overlap and