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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626 views

Do we see objects as they really are or does our brain manipulates itself?

The apparent size of an object decreases with increase in distance that's why we see rails get closer as they get farther. We don't see the rails parallel throughout their length but converging. But ...
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1answer
928 views

Myopia / Hypermetropia eye glasses inverting image on retina

As far as I'm aware, the eye acts like a pinhole camera in that it inverts the image on the rentina. This makes sense as the rays converge and form a focal point that is upside down. Myopia (...
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1answer
3k views

How do we see different colours?

Why do different wave lengths cause electrons to behave(?) differently, causing us to see different colors? What is happening at the quantum level which causes the colour black to absorb all of the ...
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118 views

Viewing totality though an unfiltered telescope [closed]

DISCLAIMER: This question is for informational purposes only and the ensuing discussion must not be construed as safety advice. There seems to be a consensus among experts that partial eclipse should ...
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340 views

Can our eyes and ears detect phase information in addition to amplitude and frequency information?

Both eyes and ears detect continuous waves that impinge upon them - electromagnetic waves in the case of eyes, and sound air pressure waves in the case of ears. The amplitude of these waves is ...
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3k views

What is Curvature of eye lens?

I wanted to know what do we mean by "curvature of eye lens", is it the reciprocal of $r$ i.e $c=1/r$ or is it synonymous to radius of curvature of the eye lens. Moreover how does aperture relate to ...
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7k views

Perception of a rapidly flickering light

Suppose a light switches on and off at a fast rate, with equal time off and on. Why do we see a light that appears only on rather than only off?
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1k views

How does the human eye knows how far the object from which the photon was reflected?

A photon is emitted from a source and reflected off an object (or objects) until it hits the human eye. The color of the object we see depends on the photon wavelength. If photon travels with constant ...
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1answer
119 views

Identifying an optics equation in a code refactoring project

I apologise if this a somewhat naive post. My knowledge of optics is limited, and I am learning on the job, so to speak. I'm a computational biologist, dabbling in a bit of physics. I'm currently ...
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3answers
9k views

How do contact lenses work?

I understand how telescope, microscope and glasses work. But how do contact lenses work?
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2answers
88 views

Difference in focus between lenses and glasses [closed]

I have both glasses and contact lenses. The prescriptions are both recent and up to date. I am 46, so I'm starting to have a harder time to focus on things that are very close to my eyes, compared ...
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1answer
93 views

Why doesn't the brain flip retinal image horizontally as well?

I was reading about the Camera Obscura and the physics of apertures, and I read that "The camera obscura produces a flipped (horizontally) image as well as an inverted (vertically) one." I understand ...
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Can two polarized glass filters held at near 90° orientation serve as safe eclipse glasses? [closed]

Using two polarized filters to block all (?) light is a common classroom demonstration. With the imminent north American total eclipse, the media has been pushing eclipse glasses and emphasizing the ...
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2answers
51 views

If someone were to put really small objects 10x spaced on a background, would they see the objects or the background?

If someone were to put a sheet full of 1 micron x 1 micron black squares as a grid on a white piece of paper, and spaced them 10 microns apart (up-down, left-right, obviously diagonal doesn't count), ...
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2answers
645 views

The ability to squint and focus - what is it called and is it used in optics? [duplicate]

Most people that wear glasses or contacts can squint to reduce the blurriness of their vision. How can this be explained, and has it ever been used in optics to enhance the focus or clarity of an ...
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1answer
102 views

Why does our eyes see red when exposed to too much light? [closed]

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?
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573 views

Hyperopia, Far Sightedness

With hyperopia, the focal point is behind the retina, shouldn't this mean that the image is flipped on the retina itself from what is usual? I must be drawing my ray diagrams wrong. A little ...
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1answer
77 views

How Vision Works [closed]

Vision works when we receive the reflected wavelength of white light from a particular object. There is a single angle of reflection depends upon the light's incidence angle. If so, how can many ...
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521 views

Why is blue darker than yellow in an analog black and white photograph?

Blue is perceived darker than yellow by the human eye, because of biological principles within the eye. I can understand that therefore, when making a picture black&white in software like Adobe ...
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1answer
130 views

Why do I see discrete images when moving an object in front of a screen? [closed]

I observed this while doing my homework. I have a habit of shaking my pen between my fingers vigorously while thinking something. My PC's screen is right in front of me (on my study table itself). ...
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1answer
117 views

What would happen if the aqueous and vitreous humour of a human's eye are replaced by some harmless transparent liquid of different refractive index?

The title says it all. What would the person be able to see? Note By harmless, I mean that it is non-corrosive, non-toxic, etc. The liquid doesn't cause any biological damage to the eye or any other ...
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3answers
810 views

Why does looking through pinhole change the eyes focal length?

Normally the comfortable viewing distance for small text on my phone is around 20 to 30cm much below that and details start to get fuzzy. However looking through a pinhole (hole punctured in a thick ...
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2answers
446 views

Why don't eye lenses alter depth perception?

What it is going to do is bend the rays so that light from infinity "appears" as though it is coinciding with a person's far point. In doing so, it allows the person to see a clear image, without ...
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1answer
656 views

Why do we see just one octave of light? [closed]

When one takes a look at the usual chart of EM spectrum one cannot help but notice that visible spectrum is slightly below one octave of frequencies; that is, the ratio between the highest and least ...
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2answers
188 views

Space station illuminated by the Earth

Let's say that we have a space station orbiting the Earth around the equator at a speed of 360 degrees per 24 hours, always being roughly on the line between the centers of the Earth and the sun. From ...
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3answers
2k views

Why electric field has a major role in vision?

Although the electromagnetic wave is made op of both electric and magnetic fields the electric field contributes much in vision and is thus, called the light vector. But, why is it that the electric ...
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1answer
130 views

Is there a one-to-one relationship between colour theories and our trichromatic vision?

This has started to bug me more and more… it involves: colour theory the trichromatic properties of our eyes through cone cells and light. Is there a one-to-one relationship between colour theories ...
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1answer
424 views

How does the focal length of the lens change the distance from the camera to an object?

I am reviewing some old image processing notes and have the following problem: I have a camera with a projection plane of $2cm\ by\ 2cm$ and a $15mm$ lens. If you want an $1.5m$ object to take ...
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1answer
3k views

Effects of high frequency lighting on human vision?

I have a couple of different LED flashlights. One of them has three different "modes" of brightness, and the way it controls it is via pulse width modulation (PWM). Here is a picture that illustrates ...
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1answer
620 views

How to determine the required resolution to view an image at a certain size?

If I have several camera specifics, can I determine the required resolution to view an image at the size I want? For example, let's say I want a picture of a square painting to be at least ...
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1answer
58 views

Refractive screen for myopia [closed]

Is it possible to create a screen for a computer monitor to allow a Myopic person to see the screen without glasses?
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1answer
2k views

Do reading glasses really need a smaller PD (Pupillary Distance)?

I've heard that reading glasses (negative number lenses but with a "smaller" prescription) need a smaller PD than distance glasses because the pupils are closer when looking at close objects. At ...
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3answers
4k views

Why do sea waves seem to be standing still when you look from the window of an airplane?

Looking from the window of a passenger plane even at moderate altitude such that one can still recognize individual waves and even something like white foam, and small boats close to the cost line, it ...
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1answer
2k views

Is near point defined for a myopic eye and far point defined for a hypermetropic eye?

I learnt about far Point of a myopic eye and near point of a hypermetropic eye. But I am confused about the above question. And if near point is defined for a myopic eye and far point defined for a ...
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2answers
350 views

WHY is a Refracting telescope image distance $S'=-\infty$?

In the above slide, it says that "Eyepiece '2' makes the image distance $S'$ approach $-\infty$." However, What I don't understand is that if I place my eye right at the Eyepiece 2, then I would see ...
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1answer
6k views

How to determine the field of view for a pinhole camera with given parameters?

I am reviewing some old material I learned years ago and am having trouble figuring this one out. Can somebody confirm that I have done my math correctly, and tell me how I can recover the field of ...
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1answer
33 views

Why is there no blue peak in the photopic luminosity function?

A luminosity function "describes the average spectral sensitivity of human visual perception of brightness". My understanding is that basically, for the same power, we perceive green light as ...
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0answers
39 views

Do virtual images exist in the real world? [duplicate]

I have been reading an article here in physics stack exchange that talks about if it is possible to see virtual images, and i read an answer saying it is actually your brain that understands the ...
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0answers
638 views

Why do my glasses make the ground look tilted?

I just started wearing glasses to correct my myopia today. I have -0.25 spherical and cylindrical power in my right eye and -0.5 spherical and -0.25 cylindrical in the left eye. Everytime I look at ...
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26 views

Inverting Horizon?

everyone knows that looking at the horizon at something going far away, the last thing you see from it is its top, but what if you had a ground going up very very very slightly and something moves ...
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74 views

Why do we see vertical lines when we close our eyes into slits?

When we close our eyes into small slits and look at a light source we see vertical lines of light coming out. Why does this happen? Is it something to do with our eyelashes or is it because of ...
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72 views

Why are distant lights more flickery in peripheral vision?

I have just realized that if you arrange your angle to a flickering distant light source and make it fall into your far-peripheral vision (+70 degree to the side of your FOV), you perceive it to be ...
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0answers
73 views

Terminology - optical (visual) properties of a structure

I am trying to understand few terminological problems that I encounter. Without knowing keywords it is hard to perform search for literature or publications in the area. The area relates to the ...
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67 views

Can a person with bad vision see a blurry picture clearly? [duplicate]

I was just thinking to myself how weird it must be to have bad vision. Then I thought, I wonder if you could print a picture that would appear clear to someone with bad vision. That seemed unlikely to ...
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304 views

Insect Eyes Vs Human Eyes?

Humans have frontal eyes. Less field of view. But better resolving power. Insects have lateral eyes. This means they have a large field of view. In some female insects the lateral eyes have much more ...
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2k views

Is there such a thing as purple light? [duplicate]

This is a question as much about color perception as the physics of light. Since I have normal vision, without color blindness, I will draw on my experiences in formulating my question. I will add ...
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2answers
855 views

Do our eyes act as observers at the quantum level? [duplicate]

This is a very high level question. I was just thinking about the idea than in quantum physics, the act of observing has a "strange" effect on some properties (e.g. double slit). If I'm staring at a ...
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2answers
123 views

Why does image noise happen?

Why are digital images shot with a high iso (which means the camera sensor is much more sensitive to light) so much grainer than pictures taken with a lower iso? Here is an example of the type of ...
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2answers
332 views

Is Invisibility possible according to physics?

Is Invisibility possible according to physics? Is there any backing theory to prove it true or false?
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How can we see stars if their apparent width is less than a pixel?

Stars are so far away that their apparent width is essentially zero when compared to any pixel of a camera or TV screen. And yet we can still see them. According to our eyes stars have a finite ...