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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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2answers
20 views

What is the optimal light setting for human vision? In other words, is my vision better during the day or at night?

There seems to me to be two main effects that should be considered in answering this question. The first is that the iris dilates in low-light settings, which causes an increase in the numerical ...
1
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1answer
87 views

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

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). ...
1
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1answer
42 views

Can visible light be composed of invisible electromagnetic frequencies?

I know that when we see red light (via electromagnetic frequencies in the red range) and blue light (via electromagnetic frequencies in the blue range) at the same time, we perceive it as magenta ...
1
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3answers
75 views

Is the yellow we perceive when our eyes are hit by red and green light at the same time the same yellow that is at the yellow frequency/wavelength?

I am trying to understand how color works, and I am curious whether the yellow we perceive when our eyes are hit by red and green light at the same time is the same yellow that is at the exact yellow ...
1
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1answer
34 views

Why do I see red light reflecting from my normal glasses when I wear anti blue-ray glasses?

Today when I went for eye checkup, the optician presented to me an anti blue ray glasses. This type of glasses reflect blue light, and hence, while wearing my original glasses and holding this new ...
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2answers
58 views

How do our eyes restructure the picture of objects “right side up”? [closed]

I hope I am posting this in the correct site. I am puzzled with the following sentence: Time and space are compressed into a point of no dimension through which images of the things around us are ...
3
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2answers
91 views

Why cannot we see too small objects with naked eyes?

Why is there a lower limit to the size of objects we can see with our naked eyes? What are the factors at work; diffraction, light reflected, resolution of eyes?
13
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1answer
4k views

How can we see a beam of light?

A beam of light is made of photons, which simply travel in a line from point $\text{A}$ to point $\text{B}$. But we can only see things when photons hit our retina, so doesn't this mean that the ...
-1
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0answers
69 views

How to tell if a color is impossible/imaginary?

Short version How can I tell if a color (e.g. XYZ) is impossible? For example, this color is impossible: XYZ: (15.96, 84.04, 0) xyY: (0.1595, 0.8404, 0.8404) Lab: (93, -196, 161) (D65 whitepoint) ...
-5
votes
1answer
56 views

Is light visible? [closed]

I was confused when i saw the rgb spectrum where the light goes on a prism and then we get the colours .. we see the source of the refracted light ? like seeing a blue sun ?
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3answers
45 views

How light help us see objects?

For example imagine we have an object in an area with wind...how the reflected light come to our eyes and doesnt travels with air (medium) ? also can the light be reflected in all directions so every ...
-1
votes
0answers
27 views

Why is there no purple in the rainbow? [duplicate]

I see from here that while green and orange are how we perceive actual wavelengths of light, purple is a mixture of red and blue. Why is there this difference? Green is a mixture of blue and yellow. ...
0
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2answers
59 views

Tiny blue and red paint close to each other result in black or magenta? [closed]

Now, if I draw two tiny spots with red and blue paint on paper and they are so close (but they do not cover each other) to each other that human eyes cannot identify there are two spots. To the color ...
1
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1answer
41 views

Does looking at someone produce any physical force?

I was driving home one day and it just popped into my head, does looking at someone or something produce any kind of physical force. If someone could answer this question that would be great.
0
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0answers
70 views

How do hypermetropic people see objects beyond the focus of their convex corrective lenses?

The way I have developed intuition about optics suggests that humans can only see objects if two rays of light that originally emanated from the same point reach the eye in a way such that when ...
1
vote
2answers
61 views

Depth of field of the human eye

When reading about the basics of photography and the physics involved, I learned about  depth of field. Long story short, the message is that with a smaller aperture, the length of the depth of field ...
2
votes
2answers
73 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 ...
0
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0answers
32 views

Why animal eyes see the spectrum from red to violet?

Maybe this would not be proper question on physics stack exchange, but it originated from physics book so I'll post it here anyway. I have much interest in color recognition evolution. I'm studying ...
6
votes
4answers
232 views

How was the Ancient Greek theory of vision disproved?

Ancient Greeks and ancient Indians believed that the way in which vision works is that a beam goes out of the eye and hits an object. Whereas now we know that light reflects off the objects and then ...
-2
votes
1answer
42 views

Is the anti-blue reflective coating on my glasses doing more harm than good? [closed]

My prescription glasses come with free anti-blue reflective coating. The idea is to minimize the exposure to blue light, which studies have shown can be damaging to eyes over time (especially if it ...
-1
votes
1answer
24 views

For nearsightedness how does the concave lens not shift the focus point for near objects?

In case of myopia, the light focuses in front of, instead of on, the retina when observing far away objects. while for near objects the eye is able to focus the light onto the retina. For most people ...
1
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0answers
31 views

How can light bulbs' flicker rates be found? [duplicate]

The flicker fusion threshold is often said to be about $60\,\mathrm{Hz}$ for humans, meaning that humans tend to perceive cycling events happening faster than 60-times-per-second as a blur rather than ...
0
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1answer
52 views

Why we see a static picture of the sea when we are traveling by plane?

This question may look stupid but it's something that came to my mind months ago when I was on a plane. When one looks through the window on a plane, there are light and dark parts of the ocean (it's ...
1
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1answer
44 views

How does the human eye not get a distorted image from an irregular object?

Suppose I have a sheet of cardboard, or for that matter any irregularly shaped object. Now we do know that reflection on cardboard is irregular and not specular as it is a rough surface compared to a ...
1
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2answers
53 views

Human eye dispersion [duplicate]

As we know dispersion is caused by a convex lens.our human eye also has a convex lens so dispersion must take place in eye also this leading to a formation of blurred image on retina.then why are we ...
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votes
1answer
76 views

Colors sensitivity by human eye and light wavelength [duplicate]

I do not understand why human eye sees different colours from the LED TV/screen. Especially violet. For example, how we get yellow color on TV. There are 3 small diodes Red, Green Blue in LED screen ...
0
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0answers
30 views

Calculate Optical-Ray Angle (in respect to optical Axis) for every Pixel on Sensor Plane

I'm currently working on designing a catadioptric image system for mobile robot systems and do think I need help with the first steps of the calculation. The design of the mirror will be based on this ...
0
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0answers
16 views

What is the most important data when measuring the 'sources' from which we perceive light?

If the JND of light for our eyes in it's most sensitive areas is easily 5nm or less, when measuring light sources, which data should be most pertinent? For instance, the attached measurement of an ...
1
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1answer
46 views

Understanding the color of fluorescent and non-fluorescent objects

I am trying to read up and understand a lot about how normal looking objects like chairs are visible to us as compared to fluorescent substances. This question says that - "It is often said that ...
0
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0answers
21 views

Why is the focal length of a camera inextricably linked to a different perspective?

The human eye can focus on different distances without ever changing the perspective. Why is the change of focal length in a camera, on the other hand, always linked to a change in perspective? Is the ...
0
votes
1answer
46 views

Why does the human eye-lens have a constant magnification for a fixed object distance?

The human eye-lens flexes to change focal length and thereby bring objects of various distance into focus. The magnification of the lens $M$ is always constant for an object with distance $d_o$ ...
1
vote
6answers
325 views

Hypothetically, if there was a substance that could absorb all visible light and reflected none, how would it appear to the human eye?

Would said substance just be perceived as a "hole" in our vision, if it was capable of absorbing 100% of all light? Also on a side note, would the absorption of all light instead of only visible ...
5
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1answer
262 views

Refraction: Swimming goggles, short-sightedness, and underwater vision

I have thought of this question due to personal experience. I am short-sighted, and over the last three years my short-sightedness has worsened. Taking a lifeguard certificate again now that I did ...
1
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1answer
59 views

Blurred vision clearer with use of 2 mirrors

I have been having trouble with my vision. blurry and shadows. I realized that when I use a hand held mirror to see the back of my hair that is being reflected by another mirror behind my back I can ...
6
votes
1answer
347 views

Dark room lights

When I lay down in my room at night it's pretty much completely dark but I observe this strange phenomenon going on. When I lay down and look at my ceiling I can see my white fluorescent white bulbs ...
0
votes
1answer
59 views

Optics and lens

I am nearsighted. So i am using glasses. In glass i see a convex shaped lens. But to correct my vision i need divergengt lens that is concave. When i am using the glass in correct position the upper ...
1
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0answers
55 views

Chromadepth glasses [closed]

I am making some 3D graphics in POV-Ray that are meant to be viewed using Chromadepth 3D glasses. These glasses make blue objects in a drawing look distant, and red objects look like they're close to ...
2
votes
1answer
48 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 ...
2
votes
1answer
59 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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3answers
85 views

What is Fourth Dimension?

Before people get pissed at me for asking a question that has likely been asked more than a few times, I just want to know a simple answer, if first dimension is that an object exists, (collision) ...
0
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2answers
61 views

I have a question about color and light

I've been thinking, imagine you have a room, a light bulb at the top and you hold your hand up off the ground. Of course, there will be a shadow under your hand and no light will have access to that ...
1
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1answer
68 views

Actual Jupiter seen from the place, will it looks like on the pictures?

Jupiter picture processed by one of citizen scientists Picture above is artificially proceeded by one of the citizen scientists working for NASA. It was composed from monochromatic pictures taken by ...
22
votes
2answers
2k views

Why do I see three 'beams' when I look to a distant light source at dark?

In the night, when I look at a distant light source (for example a street lamp a few hundred meters away) I do not simply see a spot but rather a spot which is surrounded by 'light beams'. So instead ...
37
votes
7answers
7k views

Can you be blinded by a 'dim' light?

From what I can tell, if you pick a color near the extreme of the visible light spectrum, let's say red, and trace a path across the spectrum until you are outside of the visible range, at some point ...
1
vote
2answers
95 views

How to define white color scientifically? [duplicate]

I'm sorry some of you may mark this question as duplicate, but even though I searched over about this I couldn't get satisfacory answer. Also I think this question is more related to biology, but I ...
0
votes
0answers
51 views

Optics in swimming goggles

What optical lens, coating, or some other optical feature/property can improve underwater vision or provide other underwater advantages (like vision angle) if used in swimming goggles? I've thought ...
0
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1answer
80 views

Why do I see a rainbow when looking through a slit with my fingers?

Today I was waiting in the car park and noticed the very bright sunlight reflecting off the car near me, I was just being bored and noticed when I make a small slit/hole with my fingers by curling ...
8
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1answer
159 views

Why does the moon appear fairly flat to a naked eye?

When I look at the regular ball picture the "edges" appear somewhat darker. Here's a random image I just found on image search :) Image source and that's how I can tell it's "round". Or so I assume. ...
0
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2answers
81 views

Photons and information

i just study in year 10 and might not have enough knowledge about these stuff. But what i studied in physics is a photon hits a surface and is reflected to our eyes and see what photon is reflected ...
26
votes
3answers
11k views

Why am I able to see objects within 25cm?

My book defines: The closest distance for which the lens can focus light on the retina is called the least distance of distinct vision or the near point. The standard value (for normal vision) ...