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Questions tagged [optics]

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Can both lenses of different eyes intentionally focus at different amounts

Can each lens of both eyes have different accommodation rates, or have a different focal length to view objects of different distances. I understand that this can be a problem known as Anisometropia, ...
Astrovis's user avatar
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0 answers
26 views

Visibility of a spiders web from a distance

Given that the diameter of a spiders web is, for instance, far smaller than a thread of cotton. Why are spiders' webs so visible from a distance? What property of spiders' webs makes them so obvious (...
3-14159265358979323846264's user avatar
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0 answers
30 views

light hitting the center of the retinal receptive field

In my teachers slides, it says "light hitting the center of the retinal receptive field can either increase or decrease the number of impulses fired" Is this "or" because it ...
Drita Raci's user avatar
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0 answers
25 views

Relation between image on retina and the real one: looking at the two objects that are 45 degrees apart, what's the distance in the actual image?

These are what I understand about the vision. lights come through the pupil. an inverted image of the real objects is formed on the retina. which is determined by the angles. (so (a, d) and (b, c) ...
stay stay's user avatar
3 votes
0 answers
78 views

Would using positive numbered glasses while using a computer help prevent myopia?

There are multiple web pages linking screen-time and myopia. While this is not necessarily proven, for example as shown on the NIH page here https://pubmed.ncbi.nlm.nih.gov/31943280/ , it seems ...
123's user avatar
  • 221
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0 answers
48 views

Is it possible to focus only one axis of astigmatism?

When we look at something close, we focus our eyes as a circle. But what if someone has astigmatism and focuses on something close, is it possible for the eyes to "focus" only the axis that ...
123's user avatar
  • 221
0 votes
0 answers
216 views

Do all animals with eyesight get an upside-down image on their retina, or is it right-side up with some?

here's as good an image as any for showing the thing about human vision that I am asking about: So, our retina gets an upside-down image. My question is, do all animals' eyes work this way? Or do ...
Hamish Todd's user avatar
2 votes
1 answer
211 views

Why do humans see exactly one octave of light?

The visible spectrum of light is often defined as 350nm to 700nm. On Wikipedia, it says 380nm to 750nm. Either way, the upper bound is very close to double the lower bound. This means humans can see ...
Lycodo's user avatar
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2 votes
0 answers
43 views

Eye Optics/Emmert's law: Where to place scaled copies of an object so they have identical images on the retina?

I read that the center of projection of the human eye is the entrance pupil. So given a light ray which intersects the objects position and the center of the aperture stop, all copies of said object ...
InteractiveCube's user avatar
2 votes
0 answers
64 views

How would our vision be improved if our photoreceptors were not backwards?

I'm curious to how much better human eyesight would be if the nerves from our rods and cones were correctly placed behind the receptors? Are there any Animal Models with correctly placed ...
Gabriel Fair's user avatar
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3 votes
0 answers
107 views

Why do the eyes of this cat have different colours when viewed from different angles?

Why do the eyes of this cat have different colours when viewed from different angles? Both of the eyes of this cat appear yellow when looking straight at the camera. However, when the cat looks at ...
trinitrotoluene's user avatar
0 votes
1 answer
71 views

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

Whenever we close our eyes and press our hands against them we either see some colours or sometimes some weird patterns(similar to hypnotic patterns). What is the cause of this phenomenon? Also, is ...
Feraminecarts's user avatar
1 vote
2 answers
497 views

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

I am asked to determine the resolving power of both a TEM (transmission electron microscope) and a SEM (scanning electron microscope) and given the Rayleigh formula below. $$Resolution=\frac{0.61\...
jack's user avatar
  • 221
2 votes
1 answer
35 views

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

I analyzed a bunch of microphotographs recently and used "% of image area" to describe the area of structures (chorionic villi, had to show their density in placenta). However my professor suggested I ...
Gogent's user avatar
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2 votes
1 answer
46 views

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

I looked at a light like the one shown here through a fidget spinner (I believe I was observing near where the "blades" meet the inner portion) and noticed that it appeared purple/blue, particularly ...
Julien's user avatar
  • 121
4 votes
1 answer
26k views

What is the minimal focal length of the human eye?

What is the minimum length to which the focal length of our eye can go, even when considering the blurred images too.
Ashish Ranjan's user avatar
1 vote
2 answers
141 views

Which organism can point us to the evolution of sight?

I'm trying to identify the basic biological mechanisms for sight. Could you help me with identifying any organism that has the most basic ability to see objects? Most importantly, creatures ...
Nav's user avatar
  • 573
1 vote
2 answers
417 views

Are brown eyes healthier than blue eyes? [closed]

I have read somewhere brown eyes have more melanin than blue eyes and as melanin protects our body from cancers, I thought that brown eyes are more healthier.
AScientist's user avatar
1 vote
0 answers
949 views

Is the human eye supposed to see the lense effect?

Just as the GoPro cameras, we need lenses to be able to focus. Nevertheless, we can see the "fisheye effect" on the shots taken by GoPros. I am talking about this: Is it possible to notice the "fish ...
Probably's user avatar
  • 2,438
-1 votes
1 answer
599 views

How do humans know what goes on in optical illusions? [closed]

Optical illusions are designed to deceive humans, I think. That thing is moving! It really is! It's moving! However, user Konrad Rudolph just told me what went on in a different optical illusions ...
Featherball's user avatar
2 votes
1 answer
127 views

Neurophotonics vs. Optogenetics

What is the difference between the two? I see them frequently listed together in conference descriptions but can't seem to find anything that clearly explains the difference.
Diio's user avatar
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1 vote
0 answers
229 views

GFP brightness calculation

So this question is part math, part biology, but I'm asking about the biology part here (or maybe the chemistry part). Basically I'm asking about my attempt to calculate the possible brightness per ...
Tom's user avatar
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0 votes
0 answers
23 views

Clarification of the brightness of bioluminescent proteins

One basic thing I'm not too clear on, which I would like to be clear on, is the brightness per mass unit of GFP or luciferase. I was having trouble finding a resource that would state the brightness ...
Tom's user avatar
  • 371
9 votes
1 answer
8k views

Why does my eyes see a red spot when over exposed to light?

When I looked into my projector when it was on the blue screen it left a red spot in my vision. I should not have tried it but all the colors left a red spot. Why not a blue or yellow spot was left?
Muze's user avatar
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1 vote
1 answer
10k views

How can alcohol cause blindness?

Strong alcoholic beverages (e.g. moonshine) are reported to have caused blindness amongst some people. How exactly can alcohol make someone go blind? Is that because different forms of "rubbing" ...
Ebbinghaus's user avatar
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2 votes
2 answers
1k views

Can the retina emit light?

The retina is light sensor, which converts light to an electrical signal. LEDs can both emit and receive light. Similarly, is it possible to apply electricity to retina to generate light? Simply put,...
Thaina's user avatar
  • 469
18 votes
2 answers
16k views

Why does black and yellow indicate danger?

It is a well-known fact that combination of black and yellow indicates danger or poisonousness. In western society it seems obvious this comes from bees and wasps, but it seems like many tropical ...
Probably's user avatar
  • 2,438