A question that has been puzzling me for ages Watch

A Stranger in Moscow
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#41
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(Original post by Tyraell)
but the question was 'how far are you looking'. You're not looking the distance that the light travelled because it 'looped back' on itself?
I guess so...But I still think you'd be looking 10 metres if you were looking at yourself...It'd be a different 5 metres on the way back (even if the changes were only light speed)
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Lets get close...
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#42
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you are looking 10 metres becasue you are loooking 5m to the mirror and another 5m in the mirro if u get me?
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Tyraell
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#43
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(Original post by A Stranger in Moscow)
I guess so...But I still think you'd be looking 10 metres if you were looking at yourself...It'd be a different 5 metres on the way back (even if the changes were only light speed)
Hm... I would agree I think.

As I understand it, you are looking five meters but you can 'see' 10 meters. For example, imagine you stand five meters away from a mirror on a corner which shows you somebody five meters away around the corner. You're looking at the mirror (so looking five meters away) but you can see the person who is 10 meters away.

Maybe I'm completely wrong...
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urbandervish
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#44
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(Original post by Adje)
The virtual image created is (I think) 10m away. The key word, however, is 'virtual'.
'Virtual' indeed.

Now I know this is a side note, but the interesting thing to note here is that spatial perception is literally formed within our minds (imaginations). In other words, all of these 'estimations' of distance of the 'virtual' image in the mirror are being perceived by the visual cortex of our brains ~ we simply 'sense' objects that are far away or nearby within a crammed space at the back of our brains (the size of a match box) via electromagnetic waves (photons) reaching the retina; producing neural impulses which are eventually processed by the visual cortex. We merely preceive distance.


The elements causing the effects of distance and depth in images are three; (I) Perspective, (II) Shade and (III) Motion. The image that reaches the retina as a measure of height & width is (initially) two dimensional. Depth & distance results from the fact that our eyes see two different images at the same instant. i.e. the picture that reaches each of our eyes differs from the other in terms of angle & light.*

Basically, the brain assembles (reinterprets) these two different images to form our sense of depth & distance. A wholly subjective experience.

So, exactly how accurate is our perception of our surounding (virtual) environment (world)?


*By simply extending ones right arm and stretching out the index finger, focussing on the finger while closing the left eye followed by the right eye, one will observe the finger 'moving' slightly to one side. Now, while still continuing to focus on the right index finger and by opening both eyes, if one moves the left index finger close to the eye, and since a different depth has formed in the nearest digit, one notices two images!

Similarly, if one opens and closes both eyes (one after the other), one observes that the digit situated nearer will appear to advance farther than the distant finger.
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princessmarisa
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#45
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Physically you are looking at a "sheet of glass" 5m away, but to your eyes the reflected you appears to be 10m away, that is why in small opticians they use mirrors to test distance sight.
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El Doctoré de Mystéro
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#46
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How was this debate gone on so long?

There is one answer to this question. You are looking 10m at your reflection. This is a virtual image, located 5m behind the mirror. You must focus 10m away in order to see your image clearly.

(Original post by princessmarisa)
Physically you are looking at a "sheet of glass" 5m away, but to your eyes the reflected you appears to be 10m away, that is why in small opticians they use mirrors to test distance sight.
No you aren't, the OP clearly stated that you are looking at your reflection. This is an image 5m behind the mirror. If you were "physically" looking (whatever that means) at the glass then your reflection would be out of focus.
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shuvle
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#47
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5, your looking at the light being reflected off the mirror. yes?
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urbandervish
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#48
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(Original post by shuvle)
5, your looking at the light being reflected off the mirror. yes?
Yes.
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a.sheikh
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#49
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it is 5 because people you are forgetting that the rays are not comming from the image in the mirror ... the image is a virtual one and so what we see is not real... we see rays reflected from the mirror so its 5 but in fact it appears the image is formed at the back of the mirror
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a.sheikh
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#50
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(Original post by shuvle)
5, your looking at the light being reflected off the mirror. yes?
spot on
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princessmarisa
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(Original post by El Doctoré de Mystéro)
How was this debate gone on so long?

There is one answer to this question. You are looking 10m at your reflection. This is a virtual image, located 5m behind the mirror. You must focus 10m away in order to see your image clearly.



No you aren't, the OP clearly stated that you are looking at your reflection. This is an image 5m behind the mirror. If you were "physically" looking (whatever that means) at the glass then your reflection would be out of focus.
"Physically" meaning the glass is physically 5m away.
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a.sheikh
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#52
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(Original post by princessmarisa)
"Physically" meaning the glass is physically 5m away.
no no i have to disagree with you.... the image you are seeing in the mirror is comming from where? the rays that are reflected from the mirror rigth makes you see the image and the mirror is 5m away..... thats what i say that the image itself is virtual and its not that any rays from the image are comming to your eyes.... if thats the case then you would be looking 10 m but the virtual image you see it due to the reflected rays entering your eyes from the mirror so its 5 m
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tillhm
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#53
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The question you have to solve beforehand is how you define the 'length of seeing something'.

If you consider the distance a light ray traveled without being reflected or diffused, you are 'looking' 5m.

If you consider the distance a light ray traveled without being diffused (i.e. from your body), you are 'looking' 10m (assuming you neglect the little diffusion at the mirror).
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MC REN
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#54
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(Original post by a.sheikh)
no no i have to disagree with you.... the image you are seeing in the mirror is comming from where? the rays that are reflected from the mirror rigth makes you see the image and the mirror is 5m away..... thats what i say that the image itself is virtual and its not that any rays from the image are comming to your eyes.... if thats the case then you would be looking 10 m but the virtual image you see it due to the reflected rays entering your eyes from the mirror so its 5 m
meh, i disagree with you but it is somewhat a case of definition (as tillhm mentions)

I think 10m is the more sensible answer because the image is located 5m into the mirror and that is how I think the question should be taken. If you're just considering how far light has travelled, etc, then I think teachercol made a somewhat flippant response about the failings of that as an interpretation of the question. There is certainly more 'meaning' (in the sense of perception) to looking 10m at the image than 5m at the mirror
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urbandervish
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(Original post by MC REN)
meh, i disagree with you but it is somewhat a case of definition (as tillhm mentions)

I think 10m is the more sensible answer because the image is located 5m into the mirror and that is how I think the question should be taken. If you're just considering how far light has travelled, etc, then I think teachercol made a somewhat flippant response about the failings of that as an interpretation of the question. There is certainly more 'meaning' (in the sense of perception) to looking 10m at the image than 5m at the mirror
Again, in terms of 'spatial perception,' it all depends on the circumstances.

One factor that hasn't yet been considered is whether the mirror is convex or concave. Herein lies the problem. In determining the actual ratio of 'perceived size to perceived distance,' the ratio for the former would be greater than for the latter.
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MC REN
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(Original post by urbandervish)
Again, in terms of 'spatial perception,' it all depends on the circumstances.

One factor that hasn't yet been considered is whether the mirror is convex or concave. Herein lies the problem. In determining the actual ratio of 'perceived size to perceived distance,' the ratio for the former would be greater than for the latter.
I think everyone is just assuming the mirror is plane, which I'm fairly sure is what the OP was asking about

Different types of mirrors would just shift where the image was located, the basis of the question would be unchanged though (just slightly harder to visualise), you would still have to focus at a different distance (not 5m in any case) which is how I would define how far you're seeing
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