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19

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 used as a warning signal. Of course, for this question the focus is color. Honest indications Animal coloration is usually an honest indication of their ...


8

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 able to give off light in the form of fluorescence. Since fluorescence is the emission of light by a substance (granted that substance must first absorbed ...


7

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 more toxic than methanol itself and which inhibit mitochondrial ATP production. Histopathologically, circumscribed myelin damage behind the lamina cribrosa ...


3

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 associated calculations(Rayleigh Scattering) are talking about the minimum separation of 2 light sources to resolve a given object. From this we are able to ...


3

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. Background The focal length of the human eye is the distance between the lens and the retina when an object is in focus (Fig. 1). Therefore, the ...even when ...


3

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. What is the cause of this phenomenon? The increased pressure in the eye causes activation and inhibition of cells in your retina (retinal ganglion cells). ...


3

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 tissue, but also including histological techniques) and manipulation (using light to activate, inactivate, modulate, etc neural activity). Optogenetics refers to ...


3

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 photoreceptors. According to the opponent process theory of color vision, our perception of color is controlled by two opposing systems: a magenta-green ...


2

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 another. Many Disorders can be dominant for example Huntingtons disease or achondriplastic dwarfism.


2

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 that it occupies nearly all of my field of view, and look through the spinning part at my ceiling light. If the spinner is very fast or very slow, I don't see ...


2

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 ground, and were recording the reflected light intensity, without using any lenses, to reconstruct the surface features -- your resolution would be roughly the spot ...


2

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 ability to see? And by "see" of course, I mean detect electromagnetic waves. Seeing does not imply color vision and does not imply accurate vision. It will be hard to tell really which lineage ...


1

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 report a measurement, an absolute measurement should make the results easier to interpret, not more difficult (vs. % of image area). From a quick search, it ...


1

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 it is in skin. In bright areas, skin is dark to prevent damage from ultraviolet light; in dim areas, skin is light to produce enough vitamin D to avoid rickets. ...


1

"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 interpretation of what is there is wrong. Typically this involves seeing movement where there is none as in the picture you provided. A scientific way of describing them ...


1

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 stand out it would not be an Evolutionary Stable Strategy (ESS). Let's take an example. Suppose a poisonous insect was coloured with green and brown markings. ...


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