The spectrum of the Sun as seen at sea level can be seen at https://commons.wikimedia.org/wiki/File:Solar_Spectrum.png so we can see that wavelengths around green to yellow are the ones that are the most present. The human eye seems to be more sensitive to green wavelengths (around 555 nm which is plain green) compared to others: see https://en.wikipedia.org/wiki/Color_vision#/media/File:Eyesensitivity.svg.
However the Sun appears mostly white/yellowish. I don't understand why. The human eye sensitivity for orange/yellow/blue is lesser than for green. Much lesser in case of red wavelength. So even though the spectrum is a continum of all these wavelengths why is the eye fooled toward white?
And why more toward yellow than green?
Thanks.
Answer
Note the vertical scale on the two graphs you gave: The solar spectrum at sea level is given as an intensity (power per area), and it is very nearly flat over most of the visual range. The eye sensitivity is given as a percentage, which the wikipedia page where it is used does not explain beyond calling it "normalized" and "relative brightness sensitivity." If this percentage is akin to a quantum efficiency, the probability that any one photon gets detected, there is a very natural possible explanation for this effect: If rather than a power-based intensity we use a photon number based intensity for the solar spectrum, its maximum will be at lower photon energies (redder colors) where the same power corresponds to more photons.
Perceptions are always tricky: Neither our eyes or our brains tend to function quite the way one might naively expect, in lots of ways. Hence much of the full explanation might not depend much on (photon) physics at all.
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