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Rotation or not?
Im not sure if you can say that the mirror produces an object rotation. In that case the mirror image would also show a left-right reversal. Would it not? But if I move my right hand, I keep seeing a hand moving at the right side in the mirror. At the same side in space. I think that there is nothing cognitive about this obervation. But if I would (erroneously) assume that I am watching a realistic picture (or video image) of myself, I would conclude that I moved my left hand. In the latter case my cognitive system performs a mental rotation. --Albert Kok (talk) 09:28, 2 February 2010 (UTC)
Hi! In a mathematical sense a mirror image is a reflection (or rotation in a flat plane) is it not? A (left-right) flipping of the x-axis in the X-Y plane.
If (x, y) are the Cartesian coordinates of a point, then (−x, y) are the coordinates of its reflection across the second coordinate axis (the Y axis), as if that line were a mirror. Likewise, (x, −y) are the coordinates of its reflection across the first coordinate axis (the X axis).
In a physical sense: reflection from a flat surface forms a mirror image, which appears to be reversed from left to right because we compare the image we see to what we would see if we were rotated into the position of the image.
What causes "mirroring"?
This is not a question we usually ask ourselves, somehow we imagine that the answer is obvious. The mirror causes the mirroring, or at least the reflection does. But it's a rather subtle and elusive problem (at least to me).
First of all, it is clear that that which we call a "mirror image" depends on how we rotate an object toward the mirror. If we turn it around its vertical axis, as we tend to do, we get the "backward" mirror image. But if we instead turn it toward the mirror by rotating it 180 degrees around its horisontal axis, what we see is not a mirror image at all, but one that is upside down. Left is still left, right is right.
Someone told me when I asked them about this that looking through a mirror is like looking from the position of the mirror, at the object. But this is not the case. If I put myself in the place of the mirror, I don't see things mirrored, I see them normally. So there is clearly a difference. But why is it so? After all, if I imagine the light rays that bounce off the reflective surface, it would seem to me as if they behave exactly as if they had continued beyond and "behind" the mirror surface, for an equal distance. But If I had been standing back there, behind the mirror, and the mirror had not been in place, I would not have seen things mirrored, but normally. The reason would seem to be that in that case I would have been rotated 180 degrees (or something like that) compared to when I'm standing in front of the mirror.
Yet another indication that it is our turning the object that inverts the image, and not the mirror, is the fact that the same thing happens with rubber stamps. When you press a rubber stamp against a paper or other surface, there is nothing magical about that surface that mirrors the image. To the contrary, the text of the stamp is transfered to the paper just the way it is. If you then take a look at the text on the stamp, you notice that it is in fact in mirror writing. But that's simply because you just turned the stamp 180 degrees toward you! This assumes that you turned it around its vertical axis. If you instead turn it around its horisontal axis, the text will be upside down instead. This seems to indicate that there is no absolute relationship between the mirrored text on the stamp and the unmirrored text of the stamped paper. The relationship is completely dependent on how you turn the stamp toward you.
But these are all questions. I'm still waiting for someone to explain why it is this way. --Kronocide 16:32, 16 September 2005 (UTC)
 provides some explanations, which aren't half bad. In my opinion, the current argument in Mirror#Image in a mirror doesn't provide good \ clear reasons for this, so probably should be updated and merged (see below) with this article. --Nato 04:00, 8 June 2006 (UTC)
- Thanks, Nato! I found Andreas Carl's response on that page especially helpful, it answers my question completely, I think. Kronocide (talk) 16:49, 7 July 2008 (UTC)
Merge from Mirror#Image in a mirror
I think the Mirror#Image in a mirror section there should be a "Main article: Mirror image" kind of link and only a brief summary, if anything. At the moment I can't even see a link to Mirror image. PizzaMargherita 09:08, 23 April 2006 (UTC)
Merger: Mirror Images
If there are no objections, I will merge the article on Tuesday, October 3rd, 2006, 4 weeks from today (Tuesday, September 5, 2006).
ENIAC 16:55, 5 September 2006 (UTC)
The stuff in the article right now is just an essay about how mirror images don't exist. If mirror images don't exist, this article is obsolete. If they do, the essay is wrong. Either way, that stuff should be deleted. Anyone agree?
I have added the concept of "mirror image" in chemistry. It is very important, especially in biochemistry where one image may be biologically active and the other not active at all. I would appreciate any further input to develop this concept. User: Leslie U. Harris —Preceding unsigned comment added by 18.104.22.168 (talk) 22:24, 28 October 2010 (UTC)
Why does a mirror flip left/right and not up/down?
This endlessly debated question is not covered at all adequately in this article. You can make any kind of flips head over heels, around a head-to-toe axis, or any which way you choose, and when you come back to facing a mirror, in whatever orientation, you will always perceive that the image is flipped left/right (according to your left and right). The article comes nowhere close to explaining why this is. 22.214.171.124 (talk) 01:44, 1 August 2013 (UTC)