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Colour theory has a lot to do with how the brain processes the signals from the retina, as well as the physics of how light is detected in the eyes. But broadly speaking, the additive and subtractive properties of colour result from the physics of light and its interaction with pigments, so if we were tetrachromatic we would experience them similarly. The ...

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Here are ray diagrams that show what is going on. In the top case, a weak (thin) lens doesn't have the power to pull the rays together tight enough. An object farther away than the tree would make rays converge on the retina. This is farsightedness. Remember the fundamental formula for thin lenses (using some appropriate sign convention):  {1\over ...

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Well the image is flipped on the retina (your brain fixes that), but that doesn't change if you go slightly in front or behind the focus. The rays that you draw in paraxial approximation ( parallel becomes focal, focal becomes parallel , center stays center) are simply not all in one point if you move your detection plane slightly away from the perfect ...

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It's pretty hard to research but I think (not sure) that the short-wavelength spectra may appear deep violet because of a negative green cone response. This answer also explains the apparent brightness of violet.

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This is more of a psychology question. After you start seeing things, you notice that a certain side of your vision is the part that will see your finger if you touch your forehead, and the other side will see your finger if you touch your lips. We designate the first as "up" and the second as "down". The brain just gets a bunch of signals. "up" and "down" ...

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I've heard several times the explanation that since the image is inverted on the retina, the brain has to turn it around somehow. This comes from intuitively and probably unconsciously picturing the head as something like a cabin where the brain lives, and sees on a display the image collected from the retina, image which it therefore has to turn around, in ...

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The brain turns it around. It can also adapt to other alterations of the visual field. It has nothing to do with physics.

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