Between two mirrors. Real experiment.

[Michael F. Dmitriyev]

I would like to offer one simple experiment. It can be repeated by everyone. I am interested in conclusions which it is possible to make of this experiment. In my opinion, a correct conclusions can have the important consequences.
So.
Two flat mirrors are located in parallel on distance 1 meter (this distance is not critical). Between them approximately in the middle some object is located. Better if it is a light source .
The point of observation, where your head is located also between mirrors, but is higher than object..
Now, we look at the mirrors.
The result of observation:
An infinite line of images of this object in both mirrors. This line of images has prospect.
Why?

 

[Integral]

There is not really an infinite number of images, it does fade out due to loses at each reflection. The many images are due to repeated reflections, thus each successive image further away by the distance separating the mirrors. As with your common experience things further away appear smaller. Thus the perspective of the image.

 

[Chen]

I'm more interested in this experiment: A perfect sphere is made completely of reflective material (i.e a mirror), and you turn on a light bulb at the center of the sphere. What would it look like for someone standing inside the sphere? How would the sphere react to the ligh, would it get increasingly hot or something?

 

[Michael F. Dmitriyev]

There is not really an infinite number of images, it does fade out due to loses at each reflection. The many images are due to repeated reflections, thus each successive image further away by the distance separating the mirrors. As with your common experience things further away appear smaller. Thus the perspective of the image.

If to draw optical lines between object and FLAT mirrors, then it will not be any visible repeating images. They should not be … But they are.

 

[krab]

Poof

A perfect sphere is made completely of reflective material (i.e a mirror), and you turn on a light bulb at the center of the sphere. What would it look like for someone standing inside the sphere? How would the sphere react to the light, would it get increasingly hot or something?

The light would burn out in short order because its own light is focused back onto itself. The sphere itself if perfectly reflective, would stay cool. The observer would just see a light go poof right after turn-on.

 

[Chen]

If to draw optical lines between object and FLAT mirrors, then it will not be any visible repeating images. They should not be … But they are.

Let us draw a line that is perpendicular to both mirrors and goes through the object itself. If you were watching either mirror from any point on that line, you would indeed only see one image on either side (I'm pretty confident of this). But since this is not physically possible (because you will either get in the way of the object or the object will get in your way), you must be a bit higher than the line, and that's when you start seeing multiple images. You will notice that the higher you are above that line, the greater the vertical distance is between the multiple images in each mirror. And as you approach the line, the distance approaches zero.

 

[Chen]

The light would burn out in short order because its own light is focused back onto itself. The sphere itself if perfectly reflective, would stay cool. The observer would just see a light go poof right after turn-on.

I don't understand how light can "burn out" or "go poof"... can you please explain this in more detail?

 

[krab]

If to draw optical lines between object and FLAT mirrors, then it will not be any visible repeating images. They should not be … But they are.

Don't know what you mean. Draw a line from source to eye, reflecting once off the mirror, observing the law of reflection. That gives image 1. Now draw one that bounces off mirror 1, then off mirror 2, then off mirror 1 again, then into eye. That is image 2. Notice angle of ray from this second case is different from angle in first case, so observer sees 2 images at different locations. Continue to infinity with more and more bounces.

 

[krab]

I don't understand how light can "burn out" or "go poof"... can you please explain this in more detail?

It gets too hot and melts. You have to realize that the power dumped (presumably electrically) into the light bulb has nowhere to go, since it cannot be absorbed by the sphere, which is perfectly reflecting. so the energy effectively stays in the light bulb. You can easily do this experiment. Take a 100 watt bulb, and wrap tin foil tightly around it. Or,.. don't try it. You could start a fire in the socket.

 

[Chen]

Neat... I think I'll try this little experiment tomorrow (but outside the house and with a battery). If I don't come back tomorrow, be sure not to try this yourself.

 

[Michael F. Dmitriyev]

I'm more interested in this experiment: A perfect sphere is made completely of reflective material (i.e a mirror), and you turn on a light bulb at the center of the sphere. What would it look like for someone standing inside the sphere? How would the sphere react to the ligh, would it get increasingly hot or something?

In this case the energy inside sphere will collect and events will develop on one of scripts:
1) the light source will be broken;
2) in consequence of growing thermal movement, the sphere will lose the spherical form and will be destroyed in a result.

 

[Alkatran]

Is it possible to have a sphere of material that let's light in, but not out? (The sphere would have more and more light, until the point where it absorbed it as quickly as it entered.. how hot would it be...)

I almost said "the sphere would get brighter and brighter", but caught myself

 

[Chen]

Is it possible to have a sphere of material that let's light in, but not out? (The sphere would have more and more light, until the point where it absorbed it as quickly as it entered.. how hot would it be...)

I almost said "the sphere would get brighter and brighter", but caught myself

Depends on your definition of "letting light in". If you place a battery-operated light bulb inside such a sphere, then you're basically just emitting photons into its space. You could call that letting light in, but then maybe not - because the energy already exists inside the sphere in the form of the battery.

 

[Michael F. Dmitriyev]

Don't know what you mean. Draw a line from source to eye, reflecting once off the mirror, observing the law of reflection. That gives image 1. Now draw one that bounces off mirror 1, then off mirror 2, then off mirror 1 again, then into eye. That is image 2. Notice angle of ray from this second case is different from angle in first case, so observer sees 2 images at different locations. Continue to infinity with more and more bounces.

I do not think, that this is correct explanation.
Let's simplify a problem.
Let there will be one flat mirror and one object.
Do you agree, what the image will be observed on distance 2r from object?
Here r – the distance between a mirror and object.

 

[Chen]

Do you agree, what the image will be observed on distance 2r from object?

I don't know about krab, but I agree.

 

[krab]

Do you agree, what the image will be observed on distance 2r from object?
Here r – the distance between a mirror and object.

Yes. 2r is distance of object from image.

 

[Michael F. Dmitriyev]

Then you should agree, guys, the image will be not on a surface of mirror but behind it on a distance r. Though, if we draw an optical lines, they will not leave a surface of mirror and the image should be on distance r from object. Hence, this way of reception of the image is not relevant for a flat mirror.
Let’s assume the position of object in the space as {x, y, z}
To the mirror image of object concerning a plane of mirror the position {-x, y, z} corresponds.
x=r in our case.
We note, dimension x is perpendicularly , but y and z both are parallel to a plane of mirror.
Why the mirror changes a sign on one dimension (x) only and does not do it for y and z?

 

[Chen]

Why the mirror changes a sign on one dimension (x) only and does not do it for y and z?

Because the mirror lies exactly on the YZ plane, so it only has effect in the X axis. If you were to tilt the mirror, or change the axes, you would notice it also changes the Y and Z coordinates of the image.

 

[krab]

Say origin is midway between mirrors, observer at x, object at x_o, mirror separation is 2d. THen in your notation, x_o+r=d. Distance in x-direction object to observer is x_o-x. x-component of vector of observer to images are as follows:
2d-x_o-x=2r+x_o-x
2d+x_o+x=2r+3x_o+x
4d-x_o+x=4r+3x_o+x
4d+x_o-x=4r+5x_o-x
6d-x_o-x=6r+5x_o-x
6d+x_o+x=6r+7x_o+x
8d-x_o+x=8r+7x_o+x
8d+x_o-x=8r+9x_o-x
etc...
Many times I've done these kind of calculations to find the effect of parallel-plate boundaries on the electric field of a charge distribution. It's the same problem, and there is no mystery.

 

[Olias]

Let us draw a line that is perpendicular to both mirrors and goes through the object itself. If you were watching either mirror from any point on that line, you would indeed only see one image on either side (I'm pretty confident of this). But since this is not physically possible (because you will either get in the way of the object or the object will get in your way), you must be a bit higher than the line, and that's when you start seeing multiple images. You will notice that the higher you are above that line, the greater the vertical distance is between the multiple images in each mirror. And as you approach the line, the distance approaches zero.

You are correct, I was thinking about the original poster, and gave the wrong link

Actually if you could remove/edit your post so that the 'link' is removed I would be grateful, thanks again.

 

[Chen]

Take a look at here [removed]

Click on A Photons Eye View

Very nice. Are you trying to show us something of relevance to the topic at hand, though? Because if you are, I don't get it.

 

[Olias]

Very nice. Are you trying to show us something of relevance to the topic at hand, though? Because if you are, I don't get it.

You are correct, I was thinking about the original poster, and gave the wrong link

Actually if you could remove/edit your post so that the 'link' is removed I would be grateful, thanks again.

 

[Gokul43201]

I'm more interested in this experiment: A perfect sphere is made completely of reflective material (i.e a mirror), and you turn on a light bulb at the center of the sphere. What would it look like for someone standing inside the sphere? How would the sphere react to the ligh, would it get increasingly hot or something?

The bulb would heat up and eventually melt, as Krab suggested.

But until this happens, it's interesting to note that the observer will never be able to see the mirror. This assumes that the bulb is a point source at the exact center of the sphere, the observer completely absorbs all radiation that hits him (no reflection off the observer) and there is no dispersion from the medium in the sphere. In fact, if the observer is facing away from the bulb, he will experience complete darkness ! It's plain to see this from the ray diagrams.

 

[Bob3141592]

I believe this is the design of the photon torpedo, but I'm not sure because it's been classified by the United Federation of Planets.

A sphere is made out of a hollow photonic crystal material that is transparent to light above a certain frequency but is perfectly reflective of light below that frequency. An external light source a small fraction above that frequency continuously injects light into the sphere. Since the reflection caues the light to lose a small amount of energy, it shifts downwards in frequency and immediately becomes trapped inside the sphere. Since light is continually entering into the sphere but never exiting, the total energy density inside the sphere continually increases. At some precisely timed point the energy content inside the sphere becomes so great and gets so hot that the crystal fractures, resulting in the detonation of the torpedo. And another Romulan Bird of Prey bites the dust.

I'm not sure of the details of the material that makes the photonic crystal. The physics is simple, but the manufacturing is tricky. I think they're only made on Rigel 4.

 

[Gokul43201]

Then can't the Romulans detonate the torpedo early by shining light on it - thus crippling a Federation Starship ?

Anyways the Romulan ships will probably be cloaked, so there's not much that can be done (at least there wasn't during TNG).

 

[Michael F. Dmitriyev]

You will notice that the higher you are above that line, the greater the vertical distance is between the multiple images in each mirror. And as you approach the line, the distance approaches zero.

However at any height this distance cannot exceed 2r . You only see the more perspective. This set of images exists irrespective of presence of the observer and distance between each of them is 2r.
It does not surprise you, guys?
ON ONE LINE THERE IS A SET OF REPEATING IMAGES.
It means:
1. At each following reflection the light (image) passes through each previous image not deforming them;
or

2. Between two mirrors occurs a generation of space.

I prefer the second variant.

 

[Chen]

It means:
1. At each following reflection the light (image) passes through each previous image not deforming them;
or

2. Between two mirrors occurs a generation of space.

I prefer the second variant.

Prefer what you want, but we're not in Hollywood. Personally I think you need to review the most basic meaning of the term "image" in this context, and why they are created when objects are seen through mirrors. How does the presence of an image (which is, if I may remind you, created by your eyes and completely virtual) indicate the existence of "extra space" that was "generated" by the mirrors? And in that case, why can't your logic be applied to just one mirror - everything on one side of the mirror is also seen on its other side, so new space must have been generated!

 

[Doc Al]

the virtual world of plane mirrors...

However at any height this distance cannot exceed 2r . You only see the more perspective. This set of images exists irrespective of presence of the observer and distance between each of them is 2r.

As has been explained, the images are at distances of 2r, 4r, etc from the object (assumed to be in between the two mirrors, a distance r from each). These images are virtual images. The actual light, of course, just reflects off of each part of the mirror in such a way as to appear to be coming from those virtual image locations. But from an observer's viewpoint, the light seen (assuming perfect reflection) is exactly as if the images were a string of real objects on the other side of the mirror.

It does not surprise you, guys?
ON ONE LINE THERE IS A SET OF REPEATING IMAGES.

No surprise at all--if you know what it means. Light reflects from the plane mirror as if it is coming from the virtual images in the mirror. There is a string of repeating images in the mirror, acting as virtual objects. Wherever one image would block another, from an observer's vantage point, they do--just like with real objects.

It means:
1. At each following reflection the light (image) passes through each previous image not deforming them;

No it doesn't. If you were directly in line with the object, you would not see the multiple images. They don't "pass through" each other.

Try this example: You are standing 1 meter away from a plane mirror facing directly into it; your twin brother is exactly in the same line 1 meter behind you. What do you see in the mirror? Do you see your brother? Of course not. (He's hidden behind you.) But someone else, looking into the mirror from an angle, would certainly see you both. What's the problem? It's the same with the multiple images in the mirror. How you see them depends on your vantage point.

 

[Olias]

As has been explained, the images are at distances of 2r, 4r, etc from the object (assumed to be in between the two mirrors, a distance r from each). These images are virtual images. The actual light, of course, just reflects off of each part of the mirror in such a way as to appear to be coming from those virtual image locations. But from an observer's viewpoint, the light seen (assuming perfect reflection) is exactly as if the images were a string of real objects on the other side of the mirror.

No surprise at all--if you know what it means. Light reflects from the plane mirror as if it is coming from the virtual images in the mirror. There is a string of repeating images in the mirror, acting as virtual objects. Wherever one image would block another, from an observer's vantage point, they do--just like with real objects.

No it doesn't. If you were directly in line with the object, you would not see the multiple images. They don't "pass through" each other.

Try this example: You are standing 1 meter away from a plane mirror facing directly into it; your twin brother is exactly in the same line 1 meter behind you. What do you see in the mirror? Do you see your brother? Of course not. (He's hidden behind you.) But someone else, looking into the mirror from an angle, would certainly see you both. What's the problem? It's the same with the multiple images in the mirror. How you see them depends on your vantage point.

This is the basis of a posting from the original PF of some years ago"Quantum-Relativistic Reflections".

Take your example, but this time have yourself in directly front of a mirror, you observe yourelf in the "mirror-frame". Now comes along a quick-fire artist(like ones at court proceedings), who stands at an angle, and about 2mtrs next to you, he observes and draws the image he see's upon the mirror-frame.

Now he shows you the drawn image that he 'see's', both debate as to the 'Real' image upon the mirror surface, you have argue the case because you are standing directly in front of the mirror. and see your reflection, which is difinately upon the mirror surface, you can confirm this by observation.

Now the real interesting thing is that the second observer see's a totally different image upon the mirror surface, verified by his "Quick-fire" sketch, at the mirror, 'upon its surface', we now have to overlapping images!

Now enters a 100 quick-fire artists who all take up different locations and "draw-what-they-see" of mirror surface images, whilst you still remain 1mtr in front of the mirror looking at your 'Real' image.

So now there are 101 images supported on the mirror-surface, each image occurs relative to the observer and their position, and each image must be located on the surface of the ONE-MIRROR. The question now is, for the person standing directly in front of the mirror, how many quick-fire artists does it take before the image of the person starts to degrade due to the number of "overlapping" images upon a single surface?

Simplified, is there a maximum number of different locations away from the one directly in front?..and will an observer looking at his/her mirrored reflection contain information from any of the other observers surface images.

Is there multiple 'overlapping' occurring for multiple observers, if yes then some of the image on the reflected mirror-surface, must contain "bits" of information that is not from your observation frame.

 

[Michael F. Dmitriyev]

Prefer what you want, but we're not in Hollywood. Personally I think you need to review the most basic meaning of the term "image" in this context, and why they are created when objects are seen through mirrors. How does the presence of an image (which is, if I may remind you, created by your eyes and completely virtual) indicate the existence of "extra space" that was "generated" by the mirrors? And in that case, why can't your logic be applied to just one mirror - everything on one side of the mirror is also seen on its other side, so new space must have been generated!

One mirror does not generate the space. Generation this development of something via repeating process. The reason of generation is a phenomenon of resonance.
Such condition is created between two parallel mirrors and there is no if a mirror is single.
I see the main question in this problem as :
- what distinction between an object and its image in a mirror?