When some photons in the white light from the sun are absorbed, this means some wavelengths will be missing, so how does that light still appear 'white', although some of its constituents are missing?
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$\begingroup$ How big a constituent is missing? $\endgroup$– DJohnMJun 24, 2022 at 17:47
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$\begingroup$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. $\endgroup$– Community BotJun 24, 2022 at 17:55
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$\begingroup$ Who says it is white? $\endgroup$– ProfRobJun 24, 2022 at 23:03
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4 Answers
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If sunlight is "white", then it is white by definition. A simple glance at the solar spectrum shows that it is neither flat (which would be one definition of a "white" spectrum), nor represented by a simple blackbody. Therefore the presence of any spectral features (which are in any case narrow and unresolvable by eye) cannot change the whiteness of something that is just defined to be white in the first place.
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$\begingroup$ This is pretty much it. We call the sun light "white" as it is. With all the features in it, as we talk about the sensation we call white. $\endgroup$– nasuJun 25, 2022 at 0:02
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$\begingroup$ @nasu That's the real answer: what we call "white" is the sunlight that we see, not some hypothetical spectrum without any absorption. $\endgroup$– hdhondtJun 25, 2022 at 0:28
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The absorption lines (where constituents of the hot gas surrounding the sun absorb certain wavelengths of the sun's spectral output) are 1) narrow, so in absolute terms not much of the sun's light will be missing to our eyes, and 2) distributed all across the visible spectrum so the white appearance of the light from the sun (which is due to the way our retina senses color, called metamerism) will not be skewed to one particular color or another.
answered Jun 24, 2022 at 17:56
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$\begingroup$ That answers my question. Thank you. $\endgroup$ Jul 22, 2022 at 2:21
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As the other folks have said, the absorption lines are quite narrow and the total "amount" of light absorbed is small. But we could actually expand your question. The spectrum of light arriving on the ground is not a flat spectrum.
The image above is from Wikipedia and is Creative Commons Share Alike licenced.
So, with or without the absorption lines, the irradiance is fairly "peaked" around the yellow-green part of the spectrum. So why doesn't sunlight look yellow-green to us?
The answer to that goes well beyond physics and into understanding both how the cones in our eyes respond to light and how our brains interpret the signals arriving via the optic nerve. So this actually gets us into biology and neuroscience. But, to simplify things we can just ask "how white is 'white'"? Is every "white" the same? We see and describe a wide range of subtle shading differences as white. Just look at all the different options you have if you try to buy "white paint" in a hardware store! Photometry experts will talk about the "temperature" of these different shades of white. This gets us back to physics since this is talking about fitting the spectrum to glowing black bodies which "appear white".
So, the answer to your question is, "it's complicated". If nothing else, I hope my answer points you at some additional reading which you'll find interesting.
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$\begingroup$ Thanks for the detailed answer! $\endgroup$ Jul 22, 2022 at 2:22
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so how does that light still appear 'white', although some of its constituents are missing?
(bold mine)
It is called perception of color and is tied to biophysics and complicated plots.
Note that perception of "white" comes from many components So in addition to the arguments in the other answers the fact that we see mainly white the light from the sun is due to the above correlations,
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$\begingroup$ thank you for taking the time to explain this! $\endgroup$ Jul 22, 2022 at 2:20