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7 votes
Accepted

How can alcohol cause blindness?

Methanol is rapidly absorbed not only after oral ingestion but by inhalation or after cutaneous exposure and becomes oxidised in the liver to formaldehyde and to formic acid, metabolites which are ...
Margus's user avatar
  • 186
3 votes
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Does the Rayleigh formula apply to electron microscopes or only light microscopes?

This is more than likely better asked in physics SE, however since you contextualized it biologically somewhat I will answer it here. You are correct in your concern. The Rayleigh Criterion and the ...
hisairnessag3's user avatar
3 votes
Accepted

Why do we see colours when we close our eyes and press our hands against them?

Yes, this is a biological phenomenon, not a physical one, because the phenomenon depends on a cellular response. Pressing your eyeballs (mechanically stimulating them) causes you to see phosphenes. ...
S Pr's user avatar
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3 votes
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Neurophotonics vs. Optogenetics

Neurophotonics refers to the use of light to study the brain, including measurement (i.e. microscopy, including the use of fluorescent molecules that allow measurement of ions or voltages in live ...
Bryan Krause's user avatar
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3 votes
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Why does my eyes see a red spot when over exposed to light?

You are describing the phenomenon of negative afterimages, a type of physiological afterimage, which is a result of how the cells in the retina work. Specifically, it is a result of the adaptation of ...
S Pr's user avatar
  • 6,222
3 votes

What is the minimal focal length of the human eye?

Short answer The focal length of the average, healthy, adult human eye at near-point is about 18.5 mm. Young individuals can accommodate their lenses further to a focal length of around 15.4 mm. ...
AliceD's user avatar
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2 votes

Are brown eyes healthier than blue eyes?

People conflate "Dominant" traits to mean "healthier" which is a huge misconception. The previous answer provided a good example of how what is adaptive in one environment can be Mal-adaptive in ...
Confusedbyeverything's user avatar
2 votes
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Which organism can point us to the evolution of sight?

Which is the least evolved organism that can see? The term less evolved does not mean anything. Instead one can ask Which lineage was the first to evolve the ...
Remi.b's user avatar
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2 votes
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Why do humans see exactly one octave of light?

It isn't really true that the human eye sees "exactly one octave of light". The visible spectrum does not have precise boundaries, so the choice of "350-700 nm" is a bit arbitrary ...
David Bailey's user avatar
2 votes

Why does white light viewed through optical chopper appear purple/blue?

I totally wasn't expecting to immediately duplicate this with a fidget spinner and the fluorescent light in my office. What a neat effect! My technique: I hold the spinner quite close to my eye, so ...
rob's user avatar
  • 121
2 votes

Does the Rayleigh formula apply to electron microscopes or only light microscopes?

The resolution of an SEM is not set by the electron wavelength, but rather by the size of the electron beam that is scanned over the sample. Imagine you had a flashlight scanning over a patch of ...
Raghu Parthasarathy's user avatar
1 vote

Do different microscopes and attached cameras differ in crop factor between each other?

Thus the conversion will make the results just more difficult to interpret. I'm not personally familiar with this specific measurement, but in general, unless there is a specific convention in how to ...
De Novo's user avatar
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1 vote

Are brown eyes healthier than blue eyes?

Not an answer (I hope an expert provides one), but too long for a comment. Although I'm unfamiliar with this claim, it's conceivable the optimum melanin content in eyes is subject to a trade-off as ...
J.G.'s user avatar
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1 vote
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How do humans know what goes on in optical illusions?

"Optical Illusions" or sometimes referred to as "Geometrical Illusions" aren't illusions in the sense that we are seeing something that isn't there. It's an illusion in the sense that the ...
FrankyG's user avatar
  • 509
1 vote

Why does black and yellow indicate danger?

Sorry for the late response.... I think the short answer is Game Theory. Obviously any colour scheme could in principle be used to signal toxicity. However, if a scheme was chosen that did not ...
Alex Zeffertt's user avatar

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