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Questions tagged [vision]

Physical processes involved when seeing, and comparisons between with other light detection systems. Includes questions about the eye, optical nerve, brain, corrective lenses, etc.

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7 answers
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How does light beyond the visible spectrum relate to color theory?

Like if you put a red spotlight and a blue spotlight on the same area, the light ends up magenta. And if your light is purple and you have a yellow chair, the chair will appear black because the ...
Madeira Darling's user avatar
15 votes
2 answers
2k views

Eye Floaters Optics

Eye floaters are these annoying objects floating in someones eye, usually seen by someone experiencing them as squiggly lines and dots buzzing around, either dark or partially transparent (I ...
TomY's user avatar
  • 153
1 vote
1 answer
154 views

Superposition of photons entering human eyes

Based on the Double Slit Experiment and the Mach-Zehnder Interferometer is it reasonable that a single photon enter both eyes of one person?
Bob S's user avatar
  • 19
1 vote
1 answer
56 views

What am I seeing while closing my eyes? [closed]

We all must have noticed that when we close our eyes or rub them with our hands we generally see some patterns,shapes or colors. I am still unable to understand what are these things called and whe do ...
Ishaan's user avatar
  • 517
2 votes
0 answers
56 views

Do we perceive colors through energy or photon counts?

For example, assume a light color red such that its frequency is half that of another light blue. If you were to have 1000 red photons incident on your eyes and 1000 blue photons, then the blue light ...
user2916292's user avatar
-4 votes
1 answer
85 views

Why does a ventilator appear to run leftwise and rightwise and back when spinning up?

My university professor, a friend of mine, asked me: "Do you know why, when a ventilator starts and during the process up to final speed, it runs clockwise and anticlockwise and back again to ...
George Kourtis's user avatar
2 votes
1 answer
81 views

How do we see the wave of light if we are not at the end of it? [duplicate]

Given that light is an electromagnetic wave why is it that I can see the ray of light without my eyes being in the path of the ray? For example in this image: The camera is at the side and looking at ...
Jack's user avatar
  • 31
1 vote
1 answer
39 views

Is it possible to see thermal columns?

The most common way gliders gain altitude is to circle in a thermal. Thermals are often found below cumulus clouds, or above dark areas on the ground. Without these signs, they are harder to find and ...
Yizhen Chen's user avatar
0 votes
0 answers
23 views

Is image projection a good test quality for hyperopia glasses?

I've just bought a new pair of glasses for hyperopia, and want to test the lens quality. If I use the lenses just like a magnifying glass, to project the image of a lamp onto a wall, the image should ...
Rodrigo's user avatar
  • 103
2 votes
3 answers
224 views

What is the apparent location of a real image formed by a lens? [duplicate]

Let's say I place a tennis ball 1 m in front of a plane mirror. The mirror will form a virtual image of the tennis ball, and if I look in the mirror, it appears to me that there is a tennis ball ...
d_b's user avatar
  • 8,343
0 votes
0 answers
23 views

Blue color scattering [duplicate]

I'm trying to understand, in terms of cross sections, why is the sky blue? Intuitively, blue has a smaller wavelength than the rest of the colors so it can "see" the internal structure of ...
MTYS's user avatar
  • 369
0 votes
2 answers
90 views

Light from an eclipse [closed]

Why do people fry their eyes staring at the sun during a solar eclipse? Is it that they stare at the sun for a long time---longer than if they stared without an eclipse? Or is it that during the ...
Thad_The_Man's user avatar
1 vote
1 answer
44 views

Why do we see objects with a given color?

I'm currently studying Electromagnetic Optics, and I don't quite understand the (classical) process through which we perceive an object with a given color. From my understanding, I'd make a ...
Lagrangiano's user avatar
  • 1,631
7 votes
6 answers
4k views

Why does white light appear white?

When I think of white light, I'm imagining a combination of all 7 colors of light but I believe that since light has wave nature I can say that at some point that the probability density of red light ...
Gauransh's user avatar
0 votes
2 answers
58 views

Why do the proteins in our eye have a continuous (bell shaped) absorption spectrum?

From quantum physics, I would expect that seeing e.g. red would excite the 564nm energy level of the Photopsin protein. I would also expect to only see (apart from some small smeering out) that we are ...
mtooling's user avatar
0 votes
2 answers
128 views

Why do I seem to see more depth in images when closing one eye?

I remember that when researching and learning about vanishing points and vantage points of art pieces, that by closing one eye and viewing a painting from an exact point in space, it would give this ...
vannira's user avatar
  • 103
1 vote
0 answers
48 views

What's happening, when a red and a green (laser-) light meet red glass?

I would think, that the green light is blocked and the red light travels through the glass undisturbed. Therefore what you see is a red beam, but no green beam after the glass. 'Blocking the green ...
Hoderr's user avatar
  • 11
0 votes
0 answers
24 views

Effects of chromatic aberration in the human eye

Due to metamerism, many different light spectra can be used to show a white colour. If I understand it correctly, it is even possible to make white light by combining only two monochromatic light ...
user13062187's user avatar
4 votes
3 answers
157 views

Is it possible to perceive a subatomic particle decay event with the naked eye? [closed]

The image above is to help illustrate what I observed, although in this image the line is grey, while what I saw was a bright white line. This question arises from an experience i had about two years ...
Tyler Sellman's user avatar
3 votes
2 answers
230 views

How could RGB color system compose a violet color?

In the GRB system, we combine the three primary colors, red, green, and blue, to make some new colors. It's easy to understand the production of yellow because the wavelength of yellow is between red ...
zzzgoo's user avatar
  • 141
4 votes
1 answer
69 views

Absorption respose of cones in eye

I am trying to find information about the absorption response of the cones in the eye to different wavelengths of light. I have noticed two types of graphs and answers: one which shows the S-...
Jbag1212's user avatar
  • 2,599
0 votes
1 answer
83 views

How to explain interference pattern in our eye?

Suppose we got a Lamp L that emits some light. The light afterwards hits a diffraction Grating G at a distance a. Now if you were to look through the grating with your Eye E, you were to see the ...
Leon's user avatar
  • 462
-1 votes
2 answers
58 views

How do dark color varies from people when seeing the back of their eyelids?

Depending on the light source, the back of people's eyelids either be black or dark gray depending on what lit environment they're in? the how does eyes function when people have the back of their ...
Amber Alvia's user avatar
3 votes
2 answers
949 views

Would the "FFT" of a light source be a reliable indicator of perceived color?

Paraphrasing from here: A purely monochromatic 575nm wavelength light would be "perceived" as yellow, as would a light that has equal components in red and green (but no yellow). However, ...
codecitrus's user avatar
-4 votes
1 answer
84 views

What's a safe, easily executable experiment to confirm that quantization of light occurs directly to the retina? [closed]

What's a safe, easily executable experiment to confirm that quantization of light occurs directly to the retina. We know that light is quantized when projected on to a surface, or on to an inanimate ...
it's a hire car baby's user avatar
1 vote
0 answers
71 views

Does our sense of color depend on frequency of source or the wavelength of light?

I was taught that the colors we see are results of the corresponding wavelength, but each wavelength also has a distinct frequency since speed of light is fixed for a specific medium (same goes for ...
Ashutosh's user avatar
  • 169
8 votes
4 answers
3k views

Do colours which are not visible to human eyes exist?

Are there any colours that our human eye cannot comprehend but other animals can see? The ability to see colours is the property of our eyes. For example an average dog would see less colours than us. ...
Aleph's user avatar
  • 412
0 votes
1 answer
31 views

Why does a narrow line of falling water seem drop drop when quickly looking at it from top to the bottom?

When I was under the shower I experienced when I look quickly at a single line of water falling from one pore (from top to the bottom) it looks "drop drop" instead of continuous. Why is it ...
Snack Exchange's user avatar
0 votes
0 answers
43 views

Why would an object disappear when switching from monocular to binocular vision?

I have just used a compound binocular microscope which has an ‘eyepiece graticule’ (ruler in arbitrary units) in the right eyepiece lens. If you close your left eye (or occlude the left lens), the ...
user265902's user avatar
0 votes
0 answers
40 views

Why do objects appear more obvious in a dark room when we indirectly look at them?

I am currently in my room and it's dark (of course not an absolute darkness as you know yourself). When I look directly at the ceiling lamp which has been turned-off for half an hour, I can't see it. ...
Snack Exchange's user avatar
0 votes
0 answers
37 views

How exactly can the eye detect electromagentic waves? [duplicate]

From my understanding, EM waves are traveling disturbances in the electric and magnetic fields. They travel at the speed of light, since Maxwell's equation imply $$\nabla^2 \mathbf{B} = \frac{1}{c^2} \...
HappyDay's user avatar
  • 101
17 votes
3 answers
3k views

Why is the visible light spectrum different to a hue wheel?

The following problem has bugged me for a while, ever since I noticed it. On the Visible Spectrum Wikipedia, the following is the visible spectrum: Now, in Photoshop, or really any colour picker, the ...
Tymon Mieszkowski's user avatar
6 votes
8 answers
516 views

Why specifically is looking through a telescope at the sun more dangerous than the naked eye?

At first this seems like a stupid question: "Have you never used a magnifying glass on a sunny day?!" But any lens will only ever make the focused image as intense as the target or weaker. ...
Leon Frickenschmidt's user avatar
3 votes
2 answers
120 views

Is “imperfect black”, (anything other than a black hole or vacuum), actually a color?

Is “imperfect black”, (anything other than a black hole or vacuum), actually a color? Nothing absorbs all light except for a black whole, or a vacuum which doesn’t reflect light. If we consider black ...
Name here's user avatar
1 vote
2 answers
164 views

How do our eyes perceive a parallel beam?

So if our eye is considered a lens, a parallel beam (sort of like collimated light from a flash light) should converge to a single point, the focal point. So does that mean our eye will see a finite ...
Cosmo's user avatar
  • 313
0 votes
2 answers
60 views

How do we see the picture of an object as a whole thing in spherical mirrors?

When we see an object in a spherical mirror, the different parts of the object has different pictures which are also at different locations compared to each other. The lights that go from the tip of ...
Snack Exchange's user avatar
2 votes
0 answers
70 views

Why are circular polarized 3D glasses for cinemas so cheap and working for a range of wavelengths?

Does anyone know how the filters in circular polarized 3D glasses for cinemas work (meaning how the filter on a micro-scale works, which material they use...)? Because in the lab we use of course ...
Charles Tucker 3's user avatar
0 votes
1 answer
72 views

Is it possible to design a wheel without the wagon-wheel effect?

Wagon-wheel effect is a well-known optical illusion due to the persistence of vision. It happens when the spoke of a wheel rotates to a certain position after the duration of persistent vision. ...
xiaohuamao's user avatar
  • 3,701
0 votes
2 answers
100 views

Does intense, cyclically-pulsed light appear brighter than its average?

Background The Wikipedia article on the Talbot-Plateau law mentions: If a light flickers so rapidly that it appears as continuous, then its perceived brightness will be determined by the relative ...
kando's user avatar
  • 101
0 votes
2 answers
74 views

What happens when visible light transitions to invisible light?

I was just wondering what happens when you see a visible light, for example violet, and that light slowly increases/decreases until it's not visible to the human eye. Will it fade or just become ...
parpar8090's user avatar
1 vote
0 answers
51 views

Why is each of these spectacle lenses creating two distinct refraction patterns? [closed]

Each of the spectacle lenses in this image cause two separate refraction patterns: The patterns are different between the lenses because each eye is different, obviously, but why are there two ...
spraff's user avatar
  • 5,148
-7 votes
1 answer
190 views

Insides of eyelids and light

People commonly see the insides of their eyelids and see a little amount of light and no amount of light of the insides of their eyelids depending on what environment they're in, What's the difference ...
Amber Alvia's user avatar
1 vote
1 answer
163 views

Strain on eyes when seeing a mirror [closed]

Suppose; The strain on my eyes when seeing an object at distance x is a. The strain on my eyes when seeing an object at distance ...
vivian.ai's user avatar
8 votes
6 answers
1k views

Why does the focus point of the eye does not burn the retina?

To see an object, its light rays have to meet on the retina in the focal point. But the focal point is a small white dot. Basically nothing would be distinguishable and the retina would burn because ...
StefanH's user avatar
  • 737
0 votes
1 answer
224 views

Is it correct to say that light makes things visible but light itself is invisible?

Why some books write light itself is invisible but makes things visible for us. I mean if a laser beam is passing just parallel to our eyes in a dust free environment we can't see it but the reason ...
Shinnaaan's user avatar
  • 1,357
0 votes
1 answer
172 views

Can the human eye see the images of 300 nm light on a screen through a diffraction grating?

In my textbook there is a question as follows: A diffraction grating with 200 lines per mm is placed between a monochromatic light source and a screen. The distance from the grating to the screen is 2....
Kantura's user avatar
  • 1,329
0 votes
3 answers
78 views

Finding the solid angle of a beach ball

Suppose I have a beach ball whose radius is 0.5m, and the distance between myself and the center of the beach ball is 10m. How do I go about setting up a diagram for finding the solid angle of the ...
john morrison's user avatar
1 vote
1 answer
46 views

Horizon related question [closed]

I'm a student taking an undergrad course in physics and we were discussing light and how it works in relation to vision. This question stumped us. What altitude would you need to reach on the globe ...
Arul Ross's user avatar
1 vote
3 answers
385 views

What specific properties of laser light make it dangerous?

What makes a laser more dangerous than a high powered single color LED for example? Is it the fact that it's coherent light, all the photons have the same wavelength, that it can be focused to a small ...
Plasmabot's user avatar
1 vote
2 answers
144 views

Why rays of light from different points don't form an image?

I'm asking a clarification about this questions: Why does an image only form where light rays coming from a single point get reflected or refracted and converge to a common point? I want to know if ...
Mattia's user avatar
  • 338

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