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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1answer
3k views

Purple doesn't occur in rainbow - or does it?

Usually, when asked whether the purple color exists rainbows, an answer similar to this is given: The purple color is perceived by human eyes via the activation of both red-sensitive and ...
7
votes
4answers
9k views

What is the color of a mirror?

A mirror couldn't be white, as then you wouldn't be able to see your reflection so clearly. It wouldn't be transparent, as that then won't reflect. So what color is it?
17
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3answers
294 views

How to optically rotate images in small increments (for eyeglasses)?

As the result of an accident, one or more nerves that control the rotation of my left eye were damaged. The result is that my left eye views the world rotated clockwise several degrees, compared to my ...
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2answers
638 views

The color purple in a rainbow

In a rainbow the colors order is red then orange (made from red and yellow, thus making sense that it appears in between them) the yellow followed by green after which comes blue (again green formed ...
3
votes
1answer
528 views

Why would an object appear a different size when in water?

A friend of mine has a homework question and we're having some trouble figuring out what physical mechanisms come into play for this. An underwater swimmer sees a spherical air bubble that appears ...
2
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0answers
41 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 ...
2
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4answers
453 views

What was the motivation behind suggesting the trichromatic theory of vision?

Background In this thread, I asked whether it is true that the colors red, green and blue, through additive mixture, can make up any color. Turns out they can't. However, when reading about the ...
3
votes
2answers
99 views

Is there a way to create a flickering frequency to be dependent on speed of the person looking at it?

Is there a way to make a screen or a road sign flash at different rates, depending on the velocity of the observer looking at it? I would like to achieve a state where two observers going at ...
-4
votes
1answer
53 views

is it possible to extract spectrum (color in general) from an animal [closed]

if i may ask....can this be ASAP? :3 my problem: okay this is going to sound lame, but i was wondering if it is possible to extract color (specifically spectrum) from an animal. this question ...
103
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8answers
11k views

Could Legolas actually see that far?

The video “How Far Can Legolas See?” by MinutePhysics recently went viral. The video states that although Legolas would in principle be able to count $105$ horsemen $24\text{ km}$ away, he shouldn't ...
4
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3answers
102 views

Why does the sea horizon line always seems to be at the same height as one's eyes?

I wonder why, when I look at a sea/ocean, the horizon line always seems to be at the same height as my eyes, no matter how many meters I am above the sea level. This is something I noticed when I ...
0
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2answers
72 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
85 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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9answers
6k views

Can a human size object move so fast that it ceases to be observable?

In many anime, comics, movies, etc, we see a lot of super human beings moving and fighting at such high speeds that a regular human being cannot see that they are fighting or moving pass by. In ...
9
votes
2answers
209 views

Why does the sky suddenly look gray through this window?

I am looking to the windowed roof of my building, and I notice that the sky, which has few white clouds, sometimes looks completely gray, as if there was a huge cover of gray clouds, but there are ...
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3answers
1k views

If we had three eyes, would our visual perspective be fourth dimensional?

If one covers up one eye, then he loses depth perception (two dimensional perspective). When we uncover that eye, we can now see depth (three dimensional perspective). My question is if we had four ...
0
votes
1answer
168 views

Why do objects of a given color appear white under light of that color?

Under light from the sun, a red object will scatter the red component of light, and absorb all others. Hence, the human eye perceives it as "red". White objects scatter all wavelengths of light. ...
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votes
4answers
5k views

Why is there a difference between additive and subtractive trichromatic color theories?

Helmholtz distinguished between additive and subtractive trichromatic color theories. Additive theories concern optical combinations of colored light sources and are usually modelled on RGB while ...
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0answers
23 views

Perception when Moving at the seed of light? [closed]

Let us assume that a person moves at the speed of light say towards a planet -say Neptune. Neglecting the relativistic mass effects of the person, what would be his perception? In Vsauce- a YouTube ...
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10answers
14k views

Is it possible that there is a color our human eye can't see?

Is it possible that there's a color that our eye couldn't see? Like all of us are color blind to it. If there is, is it possible to detect/identify it?
3
votes
2answers
290 views

Why does adding red light with blue light give purple light?

Our eyes contain 3 photoreceptor cells (cones) to perceive three wavelength ranges of light. Here is a visual representation of the wavelengths by these receptors (S, M and L). So if we have light ...
2
votes
0answers
84 views

-Thought Experiment- At superluminal speeds, to what degree would vision be impaired? [closed]

I was thinking about superluminal travel when thinking about advanced civilisations in the future. I was also thinking about the Doppler effect; so I decided to think about how light may be affected ...
6
votes
1answer
167 views

Why are black mosquito nets so much less visible than white ones?

I have just been installing a couple of mosquito nets for windows in our apartment. The material is polyester, fibers are approximately 0.2mm thick, and the hexagonal "holes" apprixmately 1.5mm in ...
3
votes
1answer
485 views

Are black and white colours? [duplicate]

I am an artist, and I have heard that white is a 'tint' and black is a 'shade' in the artist world. I have also heard that they are colours in the normal world/scientific world. Which is correct and ...
5
votes
5answers
377 views

What are colors?

If you go to any course about photography, you learn that all colors are made up of the colors red, green and blue (RGB). (If you mix red, green and blue light, you will get white light, or any other ...
5
votes
2answers
505 views

Are there any astronomical objects at night that are dangerous to look at (through a telescope)?

Are there any astronomical bodies that would be dangerous to my vision to view through a telescope? Obviously the sun is dangerous, but are there other bodies at night I should avoid?
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5answers
3k views

Eye sensitivity & Danger signal

Why are danger signal in red, when the eye is most sensitive to yellow-green? You can check luminosity function for more details...
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3answers
3k views

Is wearing 3D glasses from the cinema as sunglasses hurtful to the eyes?

I heard a few times that using them as sunglasses is hurting the eye since UV light is not filtered, but the pupil is wider than it would be w/o wearing them because the visible light is dimmed. I ...
3
votes
4answers
713 views

What is difference between white objects and transparent objects as far as photons are concerned?

Transparent materials let photons through because the energy gap of electron is so large that the photons cannot be absorbed. If the material absorbs a photon, the photon disappears; does this mean ...
3
votes
6answers
6k views

Limit of human eye flicker perception?

I am designing a LED dimmer using software-controlled Pulse Width Modulation, and want to know the minimum PWM frequency that I must reach to make that LED dimming method indistinguishable from ...
16
votes
5answers
3k views

Why do nearsighted people see better with their glasses *rotated*?

If you are nearsighted (like me), you may have noticed that if you tilt your glasses, you can see distant objects more clear than with normally-positioned glasses. If you already see completely clear, ...
2
votes
3answers
146 views

Why can colors be mixed? [duplicate]

We can combine colored light, creating other colors, at least in terms of visual perception. But how it the result physically "a different color" - if it is at all? Or is all this not a physical ...
0
votes
1answer
80 views

Visual Fields testing: Decibels of sensitivity - meaning

Automated Visual Field test measures the patient light sensitivity in decibels. Questions: If one point has sensitivity of 30 decibels and another point has sensitivity of 27 decibels does it mean ...
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vote
1answer
61 views

Explanation request for flashes of light [closed]

I have observed what I believe to be the same phenomenon on two occasions and wanted to ask for possible explanations. Both times, I saw flashes of whitish light, near the ceiling of a room. They ...
4
votes
0answers
45 views

How does a microscopes optics expose defects in the users vision?

I've got cataracts in both eyes. My vision is correctable to 20/30, so the cataracts are essentially a non-issue in daily living. But when I use a microscope, which I do daily, (binocular, zoom ...
0
votes
3answers
207 views

Is everyone seeing the same color as I see? [duplicate]

As the cone cells are different in numbers in people, how can we say that everyone is seeing the color as same? for example the color you are saying as red may be not the one i see as red..
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2answers
7k views

Is black a color or absence of color? [closed]

Is black a color or absence of color? When there is no light, everything is black, so how can we say that black is a color?
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2answers
875 views

At what distance could you see andromeda with the naked eye?

We've all seen the telescope photographs of andromeda galaxy: I'm wondering if it were possible to travel close enough to the andromeda galaxy could you achieve a same perspective with the naked ...
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votes
4answers
3k views

Is it only red, green and blue that can make up any color through additive mixture?

I'm reading about color vision and have some trouble understanding the motivation for why the trichromatic theory was suggested in the first place. The book I'm reading ("Psychgology: The science of ...
5
votes
1answer
3k views

How much sky do we see at any one moment?

When we look at any particular point the sky, what percentage of the celestial sphere do we see? This question arises from the notion that on average there passes one meteor per hour overhead. So ...
3
votes
1answer
904 views

Static flow of water in the presence of a loudspeaker

The title, I don't know whether it's correct or not, but I came across a video in youtube, http://www.youtube.com/watch?v=_PkgQQqpH2M. The author of video used the title and hence I used the same. ...
9
votes
1answer
185 views

Why can movies get away with 24 frames per second, but games can't? [closed]

Movies look reasonably smooth at 24 frames per second; unless the screen is huge and you use your peripheral vision, you usually can't see each frame individually. This has lead to a large amount of ...
4
votes
2answers
176 views

Difference in perception of unpolarized and polarized light

What is the difference in perception of polarized light and unpolarized light? What difference does polarized light cause to our eyes?
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vote
1answer
147 views

Experiment regarding myopic correction by a manipulation of fingers?

Here is a small experiment my tutor once told us for just amusement. It works for myopic people at least, and can be a good check to see if you have myopia. With your naked eye, ("remove the ...
4
votes
3answers
120 views

Possibility for contact lenses that enhance the vibrancy of color

Would it be possible to develop oculars that would enhance the vibrancy of color? I know there are many digital filters to improve vibrancy, but are there physical devices able to produce the same ...
5
votes
8answers
544 views

Is there a lens that would invert my vision?

Would I be able to invert my vision by mounting a particular lens in front of each eye? I am currently able to achieve this by mounting a right-angled triangular prism across both eyes. The specific ...
1
vote
0answers
224 views

How would you make 360 degree vision glasses? [closed]

Animals that have an eye on each side of their head have 360 degree vision so just like with the inverted vision glasses you can buy I'm wondering how you make 360 degre e glasses? I'm thinking of a ...
0
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4answers
909 views

What colour is nothing?

To me this is very confusing, but I hope we can discuss it and find a solid answer to the question. If you were somewhere where there was absolutely nothing, what colour would your eyes see?
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5answers
2k views

Explanation about black color, and hence color

I'm bit confused about 'black' as a color. As per my knowledge, it is not given in visible color spectra like other colors for example red, violet etc. Also I'm confused with definition of color--does ...
4
votes
2answers
263 views

Sensitivity of eye

In which color human eye is most sensitive?