20
votes
Accepted
Why does black and yellow indicate danger?
First of all, great question! What you describe here is known as aposematism. Aposematism is the adapation of warning signals against the predator. This word is used for any sound, coloring, and odor ...
- 3,079
8
votes
Accepted
Can the retina emit light?
Please allow me to start by saying I know nothing about LEDs, so my answer isn't going to address your analogy. I'm also going to keep it more simple.
Can the retina emit light?
Yes. The retina is ...
- 24.7k
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 ...
- 186
3
votes
Accepted
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 ...
- 260
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.
...
- 52.3k
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.
...
- 6,192
3
votes
Accepted
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 ...
- 44k
3
votes
Accepted
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 ...
- 6,192
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 ...
2
votes
Accepted
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 ...
- 136
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 ...
- 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 ...
2
votes
Accepted
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 ...
- 68k
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 ...
- 8,751
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 ...
- 2,474
1
vote
Accepted
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 ...
- 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 ...
- 111
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