Talk:Mirror

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wew[d ,ermkmfktrmn4gjionpt42jogpn2oy of a website on a different server. User:138.236.226.102 (attributed later)

The story about Medusa being defeated by using a mirror to avoid being turned to stone by her gaze is one example. --David Edgar 08:50, 24 October 2005 (UTC)

I've forgotten who did it, but there's that old story that... was it Gallileo? Managed to set a fleet of ships alight using polished bronze shields or mirrors to reflect the light. They tested the theory on Mythbusters and came to the conlcusion that although it is physically possible, the logistics of it make it pretty much impossible. Gemfyre 03:24, 15 January 2007 (UTC)

Contents

[edit] One-way mirrors

Concerning one-way mirrors: I read "somewhere" that you can tell if a mirror is one-way by putting a finger to the reflecting side. If the reflection of your finger doesn't touch your finger, but is a fraction of an inch offset, then it's a one-way mirror. Is this true, or just an urban legend? -- Zoe

Urban legend, I think. The distance between your finger and its reflection is exactly equal to the thickness of the glass, since you are touching the front of the glass and it's mirrored on the back - and that should be the same for both conventional and one-way mirrors. Sometimes you can detect a one-way mirror by making a "cup" with your hand around your eyes as you peer into it closely, since the "one-way" effect depends on it being darker on one side than the other. -- Someone else 02:47 Dec 9, 2002 (UTC)
The distance between your finger and its reflection is twice the thickness of the glass! Patrick 11:35 Dec 9, 2002 (UTC)

I've noticed that at least one dictionary says that one way mirrors can sometimes be called two way mirrors. O.K., but what should an intelligent person say? Dhodges 01:19, 31 Jan 2004 (UTC)

Yes, surprisingly it seems to be the same!--Patrick 09:42, 31 Jan 2004 (UTC)
Yes, a one way mirror is simply a mirror that is lit from the side you are observing from, or one without an extra cover on the reverse side. silvarbullet1 02:19, 10 June 2006 (UTC)

A beam can't be parallel on its own, it has to be parallel with something, like another beam.--ZorroIII 13:12, 2004 Sep 5 (UTC)

[edit] No such thing as a one-way mirror!

There is no such thing as a one way mirror. It it did exist, it would allow energy to flow from cold objects to hot objects in contradiction to the laws of thermodynamics. Imagine a cold room separated from a hot room by a one way mirror. The mirror reflects the energy from the hot room back inwards, while allowing the energy from the cold room to pass into the hot room. You could run an engine (or thermocouple) off the temperature difference. Voila! Free energy! Perpetual motion! Reversal of entropy!

  • Mirrors reflect....light.
Light and heat are all the same thing, moron. CGS 20:14, 20 Feb 2004 (UTC).
Yeah. Right. Too late to get a refund on that thermodynamics course? That grammar course? That finishing school? -- Nunh-huh 20:53, 20 Feb 2004 (UTC)
I'm a computer scientist, not a physicist, and I've never studied thermodynamics but I even I know that light is a form of electromagnetic radiation and that heat can travel by electromagnetic radiation. Travel through a one way mirror, for example. What's wrong with my grammar? CGS 10:16, 21 Feb 2004 (UTC).
The phrase "X and Y are all W" would pull most people up short: generally it would be said that "X and Y are both W". It's not frankly wrong, just unidiomatic. Fine for a talk page, and wouldn't have provoked comment if not preceeded by a false assertion and followed by a rude epithet. -- Nunh-huh 21:38, 21 Feb 2004 (UTC)

What does exist is a partial mirror. The reflective coating allows some percentage of incident light to pass through, some percentage is reflected back (and some percentage is absorbed). When one side of such a mirror is dark and the other side is light, one side sees through, the other side sees their own reflection.

  • And these partial mirrors are called one-way mirrors. Etymology is not meaning. -- Nunh-huh 20:07, 20 Feb 2004 (UTC)

The article once said (before I deleted this paragraph):

Note that a one way mirror that only allows light to pass in one direction does not exist. It would allow energy to flow from cold objects to hot objects in contradiction to the laws of thermodynamics. Imagine a cold room separated from a hot room by such a mirror. The mirror reflects the energy from the hot room back inwards, while allowing the energy from the cold room to pass into the hot room. You could run an engine (or thermocouple) off the temperature difference. The result would be free energy, perpetual motion, reversal of entropy!

It's certainly something interesting to think about, but somehow I think that trying to explain one-way mirrors (really pretty simple) in terms of thermodynamics (too few people have a correct understanding of it) is not very helpful. (EditHint: Perhaps move to a physics article -- perhaps http://wikibooks.org/wiki/Thermodynamics ?)

And this explanation in particular is incorrect. It wouldn't violate thermo if the mirror uses the temperature differential to extract energy *from* the 2 rooms (or obtained energy in some other way) (dumping some heat in the cold room), then used that energy to preferentially send visible light in only one directions. Are television cameras impossible ?

There's no such thing as an empirical law: One cannot proscribe anything based on inductive edict, much less consider it. And yes, there is such a thing as a "one-way mirror"; it's called a matter and|or energy attractor. (Despite the name, it can also repel, as seen in the accelerating Hubble flow.) As I explained in my treatise Refutation of Thermodynamic Laws submitted to the free_energy eGroup over a year ago, which no one could refute, and following posts a tunable optic and sonic black hole can and does violate the increasing entropy law. Of course it's easier to narrow the kinds that go one way for a given object/system, but cases already exist. lysdexia 09:09, 20 Oct 2004 (UTC)

From the point of view of the effect that people would like to achieve a true one way mirror is entirely possible, the only thing that the laws of thermodynamics prohibit is a passive one way mirror. There is nothing that would prohibit an active one way mirror that had an external power supply.

I'd like to see some info also added here about chromatic mirrors. ie, mirrors that selectively reflect/transmit based on wavelength. unfortunately I don't seem to have the time... --Morbid-o 15:50, 20 Jun 2005 (UTC)

I've readded a phrase about the thermodynamic implications of a one-way mirror since I think it's very relevant.192.129.3.196 12:27, 29 April 2006 (UTC)

[edit] mirror-like objects

I've seen some interesting ... um ... mirror-like objects. Instead of trying to evenly put a layer of some incredibly precise thickness all over the glass, it has (when you look closely at once side) small silvery metal polka-dots all over the glass (like halftone). That makes it easy to understand that *exactly* the same percentage of light that is transmitted one way is also transmitted the other way (it's the percentage of unobstructed clear glass). But the percentage of light *reflected* one way is *different* than the percentage of light reflected the other way. (When you look closely at the *other* side with a magnifying glass, you see exactly the same pattern of polka-dots, but they are black paint). Someone painted large advertisements on the windows of local city buses in a similar way. On the outside the polka-dots are all different colors -- from a distance they blur together into some advertising image. On the inside of the bus, the windows just look heavily tinted until you look closely and see the all-black polka-dot pattern.

... or is it just so dark inside the bus that the sunlit scene outside swamps the colored dots ?

-- DavidCary 03:17, 12 Jun 2004 (UTC)

[edit] glass is easier to scratch than aluminum

The article currently says "Front silvered mirrors, where the reflecting surface is placed on the front surface of the glass, have a better image quality ..." which is excellent, but then it goes on to say "... but are easily scratched and damaged."

I don't think that's the real reason.

I always thought aluminum was *stronger* than glass. That's why people make mostly-aluminum airplanes, instead of mostly-glass airplanes -- right ? So wouldn't it be *more difficult* to scratch a slab of glass protected by a front coating of aluminum ?

-- DavidCary 02:01, 12 Jun 2004 (UTC)

"Stronger" is perhaps too vague a word. Glass is harder than aluminum, but aluminium is tougher than glass. (See [1]) In other words, a car built of glass would shatter under stress, but at least it would resist being keyed. :) --Arteitle 08:25, Aug 18, 2004 (UTC)

[edit] Mirror Manufacturing

There seems to be plenty on the "what mirrors are made of" but little on the how they are made. I'm interested in the heat processes used in the manufacturing of mirrors. What kind of ovens do they use? How much heat do they need to see and for how long?--68.213.45.251 13:50, 1 Oct 2004 (UTC)David

I agree. I've reorganized the manufacturing section, but there's a lot to be added (e.g. details on different coatings, why choose Aluminum over Silver or vice versa, shaping non-planar mirrors, etc). --Dan Griscom (talk) 03:55, 1 January 2008 (UTC)

[edit] "right-reading" mirror

Cecil Adams in an old Straight Dope column ([2]) mentions the existence of a mirror which doesn't reverse the image. He says "I'm told that somebody has designed a mirror that uses a complex combination of concave and convex surfaces (although presumably still basically spoonlike) to produce a "right-reading" image--a mirror, in other words, that shows us not a "mirror image" of ourselves, but rather the appearance we present to the rest of the world." Does anyone have any information on these mirrors, or an external link?

-- Jackdavinci 23:32, 11 Oct 2004 (UTC)

Yep, and they're not nearly as complex as he supposed. The True Mirror is just a pair of regular flat mirrors joined at a 90 degree angle. This lets one see himself or herself just as others would, which is possible because this is reversing the image left-to-right, which normal mirrors don't do. Cecil was somewhat unclear about that in his article. --Arteitle 05:43, Oct 12, 2004 (UTC)
I think something about such mirrors needs to be in the article. -Rolypolyman (talk) 17:23, 22 January 2008 (UTC)

[edit] Applications - Image

Image:Francescadani mirror.jpg
Girl looking at herself in the mirror.

Firstly, I'm not sure this image is necessary. It looks to me like someone is basically using it to advertise. Also, given the potential copyvio, as well as anyone who might innocently visit the site stamped on the picture, I think this image needs to go. --Morbid-o 15:48, 20 Jun 2005 (UTC)

ok, moved here for now. --Morbid-o 15:40, 23 Jun 2005 (UTC)

A few lines about physics would be nice...it's not obvious why light,an electromagnetic wave, reverses its direction when hitting a mirror.

Stefan Udrea 15:48, 11 October 2005 (UTC)

[edit] Practical Tips

It would be nice to see some practical tips on buying mirrors - like how to test the quality of a mirror.

I usually stand a foot away and look at objects about 3 feet behind me and at the level of my feet - if these slightly distant objects which are also at an angle appear clear, I consider the mirror to be of a decent quality.

Of course, there are multiple ways of testing mirrors. One is the 'granny tips' method (as above), and there's technical methods too - I'm sure mirror manufacturers have some quality testing procedures. Mirrors might also come with same quality rating or reflection rating.

Sam

[edit] The first man-made mirrows

It would be nice to see something about the first mirrows made by men. It seems that during Ancient Roma times, all the mirrows of the upperclass Roman people were imported directly from China by way of the Silk Road (as well as the silk itself and other luxury things). That is, Roman people did not know how to make one of them by themselves... but Chinese people knew. 81.203.157.106 20:12, 14 June 2006 (UTC)

[edit] One-way mirrors/glass

Image:Electromagnetic spectrum.JPG
Electromagnetic spectrum with visible light highlighted

The article says:

Contrary to popular belief, one-way mirrors that function well between equally lit rooms do not exist. The laws of physics do not allow for real, passive one-way mirrors (i.e. that do not need external energy); if such a device was possible, one could break the second law of thermodynamics, and make energy flow from a cold object to a hot one, by placing such a mirror between them."

Essentially a reference to Maxwell's demon. When I first read it, I thought "darn, I guess it's not possible". But now that I think of it, I think the sentence is too simplistic. The sentence alludes to externally-powered devices, which seems plausible, but maybe aren't even necessary? We're only concerned with light here, not all forms of radiation, so as long as the energy is still moving equally in both directions, the light can be going in only one. If the light in one direction was absorbed by objects on the other side, and re-emitted as blackbody radiation which traveled backwards through the mirror, for instance, that might work. Anyway, it seems like an oversimplification. — Omegatron 05:25, 9 July 2006 (UTC)

The statement is generally correct, but perhaps a bit oversimplified. Thermodynamics makes it impossible to make a true broadband passive one-way mirror. I recall seeing the proof of this years ago in an undergrad physics class, so the claim is a standard one for which references could be found if necessary. You seem to be thinking of light and blackbody radiation as two distinct things. All blackbodies at greater than absolute zero will emit some visible light, and at high temperatures they can emit quite a lot of visible light. If you separate two blackbody cavities that are initially at the same temperature with a "one-way mirror", you won't have thermal equilibrium. To achieve equilibrium, one of the cavities would have to become at least slightly warmer than the other, which would violate the laws of thermodynamics. You can imagine a solution in which the mirror transmits infrared better in the direction in which it reflects visible light, so that the energy flows balance. This probably still won't work, though, because the choice of blackbody temperature is arbitrary. The mirror must not violate the laws of thermodynamics for any choice of temperature for the two blackbody cavities. Both cavities could be "white hot" (emitting strongly in the visible), or even hot enough that their emission peaks in the ultraviolet. The mirror has to allow equal energy flow between two cavities at the same temperature, regardless of what that temperature is.
It is certainly possible to make a narrowband "one-way" optical device, however. A Faraday isolator can do this over a very narrow range of wavelengths, such as a laser line. I haven't thought about how this avoids violating thermodynamics. I presume there's a simple explanation that makes use of the extremely narrow bandwidth.--Srleffler 04:17, 17 July 2006 (UTC)
I'm well aware that you can't make a device that works perfectly and for all frequencies. That's what the article says and I think that its status as a "standard undergrad physics problem" is the reason it's being brushed off as impossible without actually thinking about it.
For a useful mirror, you only need to transmit/block visible light. As far as the electromagnetic spectrum is concerned, this is a narrowband device. So whatever's working for the Faraday isolator could work for this, too.
For comparison, imagine that the boxes are separated by a perfect, Maxwell's demon, broadband one-way mirror, but only halfway. Energy can freely flow in both directions through the other half of the passageway. Does this violate any laws? What if the passageway is then blocked off completely, but only for half of the spectrum?
Blackbody radiation is a statistical spectrum of many different frequencies, some of which will always be able to flow through the theoretical mirror, regardless of temperature. I have a hunch (just a hunch) that the energy will "find a way" to even out in every situation. The second law also doesn't prohibit a temporary decrease in entropy, as long as the long-term trend is towards equilibrium. There are a lot of loopholes.
I'm not talking about an ideal, perfect device that works for all frequencies. I'm talking about a practical, useful device that works for only light, or another selected portion of the spectrum. There are no other assumptions. The device might not be 100% efficient at blocking/transmitting light. 99% is fine for a useful device. There are no assumptions about how the mirror itself absorbs and re-emits heat, etc.
It's not a very good analogy (since energy is eventually traveling from a very hot object to an enclosed area that is much cooler), but consider a greenhouse while thinking about it. — Omegatron 12:36, 17 July 2006 (UTC)
It turns out that a Faraday isolator is not a counterexample. See, for example
Rayleigh, On the magnetic rotation of light and the second law of thermodynamics, Nature (London), Vol. 64, p. 577 (Oct. 10, 1901).
This paper is cited and discussed here. It turns out that the fact that a faraday isolator does not return the rejected light to its source is important. Any optical setup that allows the rejected light to be returned to its source would also open up a "leak" through the isolator. Faraday isolators don't violate the laws of thermodynamics, and it appears that they would not do so even if they were broadband devices.
Regarding your argument above, and your "hunch". The problem is this: the only way nature can "find a way" to even out the energy flow is by varying the temperature of one of the two blackbodies, because that's the only variable there is. The spectrum of a blackbody is determined solely by its temperature. Any such temperature variation could be used to violate the second law. I now don't think that it matters how narrow the spectrum of the one-way mirror is. Any true, passive, one-way transmission would violate the second law.
Please remove the "dubious" tag. This is an interesting issue, and I'll be happy to continue discussing it here, but the position you are proposing is original research, and so should not be reflected in the article (unless some new evidence comes up). Please do not restore to my last version of the text, just remove the dubious tag.--Srleffler 15:17, 17 July 2006 (UTC)
 ?? But your own reference says that it's possible. "With such an isolator, I could construct a one-way window such that I could see you but you not see me." — Omegatron 02:35, 18 July 2006 (UTC)
Crucial detail: It's a one-way window, not a one-way mirror. This goes to the core of Rayleigh's argument. You can have a device that only transmits light in one direction. You just can't have one that does that and returns the rejected light to its source.--Srleffler 05:27, 18 July 2006 (UTC)
Aha. All I was concerned with is the one-way transmission. So the one-way window is absorbing the incident radiation in one direction and re-radiating the energy into both chambers? — Omegatron 06:00, 18 July 2006 (UTC)
There are several different designs. Some Faraday isolators absorb the rejected light. Others emit it out of separate apertures in the sides of the device. Rayleigh's contemporaries thought that you could just set up mirrors to take the rejected light from the latter type of device, and inject it back into the chambers. Rayleigh showed that if you did this it would cause the isolator to "leak".--Srleffler 12:11, 18 July 2006 (UTC)
Because it would allow light to "backflow" through the "exhaust port" and end up in the other chamber, right? It's a little hard to understand their description without an image. In my mental image, the non-absorptive device would still be violating laws.
Maybe we should work on improving the Faraday isolator article. — Omegatron 13:48, 18 July 2006 (UTC)
Yes. If the "exhaust port" directs light back to the source it came from, light from that source can follow that path in the opposite direction. Because of the "one-way" properties of the Faraday rotating element, though, that light (which enters through the "exhaust" port) ends up going to the other source, so that the Faraday isolator no longer prevents transmission of light in that direction. No laws are violated. To really consider the nonabsorptive device properly, you have to consider all four ports, and include the environment that the two exhaust ports dump light into. Clearly the isolator will only function as expected if the environment outside the exhaust ports is darker (or colder) than the sources on the other two ports. If the exhaust environment is warmer than one of your sources, you get a net flow of energy in through the "exhaust" port. Note that if you just ignore what happens to the light dumped out the "exhaust" ports, you are essentially treating them as an infinite sink for energy. You then no longer have an isolated system, and the second law of thermodynamics does not apply.--Srleffler 03:39, 19 July 2006 (UTC)

[edit] Extraordinary section - should go in a Lewis Carroll museum or start a WP museum

Has anyone noticed that ridiculously long passage about "how we think we ought to see ourselves" in mirrors? Does this make sense to anyone? It seems like utter babble and ranting about absolutely nothing of any scientific quality. Someone with a greater knowledge of this subject should edit it. Saeghwin 04:35, 4 August 2006 (UTC)

I had never read this article before but, now that I have, I have to agree with Saeghwin, it is an absolutely amazing piece of nonsense. Lewis Carroll would have been proud of it! Yes, it needs someone with a bit of expertise in writing on such topics to produce a few pithy lines that would substitute this WP curio and then we could start a WP museum page and this could go in proudly as the first exhibit. - Ballista 05:12, 4 August 2006 (UTC)

[edit] X ray mirrors

Should the large para about nuclear bombs detonation actually be on this page about mirrors?. Maybe it would fit better at nuclear bomb--Light current 16:32, 7 August 2006 (UTC)


[edit] Cut from page for refinement

Imagine you had a complete copy of your body that you could manipulate into different positions, and imagine that it is directly in front of you and facing the same direction as you, so that you are looking at its back. If you twist the copy around the vertical axis, as if it were turning to face you, and then compare that with your reflection in the mirror. The reflection will be different from the model because everything that should be on the left will be on the right. But imagine instead that you twist the model about a horizonal axis, as if it were doing a handstand. The model would be upside down, facing you. If you compare this to yourself, and the reflection, then left and right are all correct. Your wedding ring, eye patch, and false leg are all on the correct side, be that east west north or south, but something is glaringly wrong about the reflection compared with the model, the reflection's feet are down at the bottom, where its head should be! Or, you could just keep the model in front of you so that you are looking at its back, and compare that with the reflection. Now left, right, up and down are all correct, but the reflection has its back where its front should be. The model represents the way the 'real you' ought to look. If some other person looks at you, what would they see?. So you compare the reflection against what you think you 'ought' to see. If you think you ought to see what you look like when you're doing a handstand, then the reflection is upside down, and if you think you ought to see your own back, then the reflection is flipped front and back. But most people want to see themselves from the front, whilst standing up, they think their reflection ought to look like they would look if they turned around, and they think that left has been flipped with right. In some sense what has 'really' been flipped is front and back. If you were to describe the body with co-ordinates, east/west north/south up/down, and the mirror has been facing south whilst you are looking north, then the difference is in the north/south direction; front and back. So I don't think my reflection looks a bit wrong because left has flipped with right, I think it looks hideously deformed because it has a face where the back of its head should be.

--Light current 16:40, 7 August 2006 (UTC)

Well done & thanks, 'Light current' - It's good to have taken this lot out for reworking - however, I feel there is still need for greater clarity in what's left in the article. I feel that most of it's in need of a pretty hefty rewrite, all round but it needs to be done by someone with greater technical know-how than I have, for technical accuracy. - Ballista 16:56, 7 August 2006 (UTC)

I certainly agree that far more clarity is needed possibly involving a complete rewrite of this section. I dont feel confident or knowledgable enough either ATM, so I just thought I'd start the ball rolling by removing the worst bits! Feel free to hack the rest of it about. Maybe we should take the rest of it out pro tem?-- Ill try to help where I can 8-)--Light current 17:26, 7 August 2006 (UTC)

Thank you for editing this. Saeghwin 17:55, 7 August 2006 (UTC)

Maybe the above could be used on psychology of vision or some such page? 8-)--Light current 18:03, 7 August 2006 (UTC)

[edit] Images in plane mirrors

Rays from each and every point on the body travel to the mirror and get reflected into the subjects eye from the point you are directing your eye towards. There is no swapping over of the rays in transit to/from the mirror (you'd need a pinhole or a lens to do that). Therefore, the left side of your body forms a vitual image behind the mirror and to the left. The right side of your body is shown on the right, the top at the top, and the bottom.... etc. Think of your self as rotating in front of the mirror: When your body is horizontal, your 'left' side is at the bottom, right at top etc. You wouldnt expect it any other way would you?

This is therefore a NON PROBLEM and not really a paradox. Maybe all mention of it should be deleted and ref made to the optics pages.--Light current 17:50, 7 August 2006 (UTC)


[edit] Not salvagable

cut from page ass not really salvagable. Maybe someone else can mak it make sense?

For an object with approximate reflection symmetry, a reflection in some mirror plane corresponds to a combination of:

  • a translation if the mirror is parallel to the symmetry plane of the object, and otherwise a rotation about the line of intersection of the two planes by an angle which is twice the angle between the two planes
  • a reflection in the approximate symmetry plane of the object (due to the assumption this is a minor change)
We can apply this to the image in a mirror of, say, a standing person, because people have approximate bilateral symmetry. The image is the most realistic if it is still vertical, i.e., if the rotation is about a vertical axis. This is the case if the mirror is vertical. In this case the image of the person is in normal standing orientation and vertically in a normal position, at a horizontally different position and with an orientation rotated about a vertical axis, the latter except if the mirror is parallel to the approximate symmetry plane of the person. In particular, if one looks at one's image in a vertical mirror in left-right orientation, the image corresponds to a rotation by 180° about the vertical axis in the mirror, combined with a reflection in one's approximate symmetry plane.

[edit] Top to bottom reversal

Why does the mirror reverse left to right and not top to bottom? The answer is that it actually does reverse top to bottom.

The mathematical or geometrical version of the question is: "why does a chiral object (such as a right hand or glove) appear as an object of opposite chirality (left hand or glove) in the mirror?" The answer is that chirality of the three-dimensional space is dictated by the choice of the directions of the three axes. When the direction of one axis is reversed, as is the case in a mirror image, the chirality (or "handedness") of space changes to the opposite one. If two mirrors are set side by side (with, say, a 90° angle between them), the axes in the doubly reflected image are inverted twice and the "handedness" of the image is not changed. In such a double mirror, a right hand looks like a right hand. This set-up lets you see how you really look, but most people find it very difficult at first to use a mirror like this for shaving.

--Light current 17:56, 7 August 2006 (UTC)

If you stand in front of a mirror and point to the left the image also points to the left. However, if you point towards the mirror the image points back at you, so the image is actually reversed in and out rather than left and right, although it all seems to be a matter of perception. See Herefor a better explanation.Richerman (talk) 15:03, 10 January 2008 (UTC)

[edit] Safety and easier viewing section

Most of the stuff under this heading doesn't seem to match the heading - it needs tidying up.

--Stevenayre 12:58, 6 September 2006 (UTC)


[edit] Technology: Television and Projectors

With HDTV becoming more of a staple of consumer electronics, I thought that it was worth noting the information that I inserted under this heading. The two paragraphs are as follows:

Microscopic mirrors are a core element of many of the largest high-definition televisions and video projectors. The most common technology of this type is Texas Instruments' DLP, citation needed. A DLP chip is a postage stamp-sized microchip whose surface is comprised of an array of millions of microscopic mirrors. The picture is created as the individual mirrors move to either reflect light toward the projection surface (pixel on), or toward a light absorbing surface (pixel off).
Other projection technologies involving mirrors include LCoS. Like a DLP chip, LCoS is a microchip of similar size, but rather than millions of individual mirrors, there is a single mirror that is actively shielded by an liquid crystal matrix with up to millions of pixels. The picture is formed as light is either reflected toward the projection surface (pixel on), or absorbed by the activated LC pixels (pixel off). LCoS-based televisions and projectors often use 3 chips, one for each primary color.

As far as leading the Technology section; I'm sure it seems a little egotistical of me to put it at the top of the list, but I felt that being consumer driven technology rather than medical or military, it would be relevant to a greater number of readers. --Atomicskier 00:38, 29 December 2006 (UTC)

[edit] Two-way mirror

The article does not mention two-way mirrors. —The preceding unsigned comment was added by Frap (talk • contribs) 08:27, 29 January 2007 (UTC).

It does - one-way mirrors.-69.87.200.211 12:19, 15 May 2007 (UTC)

[edit] White surface vs. mirror reflectivity

If an ordinary mirror only reflects about 80% of the light, what is the range of overall reflectivity of visible light of ordinary white surfaces? Seems like important and relevant comparative info, for situations where imaging is not important (or not desired).-69.87.200.211 12:19, 15 May 2007 (UTC)

It looks like white paper can reflect up to at least 90%, so white surfaces seem to easily be as reflective, or more, compared to ordinary mirrors.-69.87.200.211 12:56, 15 May 2007 (UTC)

Yes, but there is a bit difference between specular reflection and diffuse reflection. Timb66 23:27, 15 May 2007 (UTC)

I think most people would be surprised to learn that a good white surface reflects more total light than an ordinary mirror! And, I think the 80% figure is so important that it needs a source reference, which hopefully would give a range for typical household mirrors. Also, it would be good to give a range of reflectance for ordinary black surfaces -- I'm guessing it is quite a bit more than the ~0% an ordinary person would assume? (If you are wondering why the Mirror article has to cover all these matters, well, I can't find anywhere that does -- so we need to pick somewhere, and gather the appropriate info, and link to there.)-69.87.204.241 17:17, 16 May 2007 (UTC)

[edit] Reflectance Table

  • Colors
70-80% White
70-80% Light cream
55-65% Light yellow
45-50% Light green
45-50% Pink
40-45% Sky-blue
40-45% Light grey
25-35% Beige
25-35% Yellow ocher
25-35% Light brown
25-35% Olive green
20-25% Orange
20-25% Vermilion red
20-25% Medium grey
10-15% Dark green
10-15% Dark blue
10-15% Dark red
10-15% Dark grey
  • Materials
95% Mirror
80% Plaster
65-75% White enamel
60-75% Glazed white tiles
60% Maple
60% Birch
40% Light oak
15-20% Dark oak
15-20% Dark walnut
15-40% Concrete
5-25% Red brick
2-10% Carbon-black
6-8% Clear glass
  • Lighting design
60-90% Ideal Ceilings
35-60% Ideal Walls
30-50% Ideal Countertops

-69.87.203.133 01:08, 25 May 2007 (UTC)

[edit] Signal Mirror?

I was just looking for a reference to signal mirrors--used by sailors or outdoorsmen to alert rescuers to their location. This topic might be a useful addition. Fagiolonero 02:29, 10 August 2007 (UTC)

[edit] Magic

What does a mirror have to do with a magic trick?--Kingforaday1620 22:33, 17 August 2007 (UTC)

[edit] One-way Glass

Would it be possible for someone fluent with Optical Coatings to have a look at One-way Glass? It would be helpful to have the input from an expert on what the actual reflective substances are in this case and how they are applied to the glass. Also, I admit that I tend to understand its use from a Security point of view and balance is required in the article. Exit2DOS2000•T•C• 07:50, 3 September 2007 (UTC)

[edit] History of the Mirror

There is absolutely nothing on this at all! Johnbod 19:20, 7 September 2007 (UTC)

  • I came here to make exactly the same comment. Yes, a history section is sorely needed in this article. Matt 03:09, 7 November 2007 (UTC). —Preceding unsigned comment added by 86.150.101.125 (talk)

I started it based on what was in How It's Made episode 305. Cburnett 21:06, 2 December 2007 (UTC)

Kudos to the string of recent anonymous users who greatly expanded the history section! Glad I could start it.  :) Cburnett (talk) 05:33, 13 December 2007 (UTC)

[edit] Can you put a mirror Online?

Is it possible to have a mirror online where you can see yourself?

Thanks, Lisa —Preceding unsigned comment added by Thinklisa (talk • contribs) 17:12, 31 October 2007 (UTC)

Nope. A computer monitor cannot actively reflect light, only generate it. Of course, the front surface of the monitor can be reflective but the amount of reflectivity cannot be controlled. You could horribly fake it with a web cam but I'm sure that's not what you're wanting. Cburnett 20:48, 2 December 2007 (UTC)

[edit] Mirrors and Animals

I have restored the list of animals in this section which was deleted by an anonymous IP address without explanation. I have left out the African Grey Parrot which seems to be a later addition to the original list and is most likely a joke. It is certainly not mentioned in the New Scientist article which is given as a reference for this section and it is flatly at odds with the text which specifies large brained animals.

Spinningspark (talk) 01:38, 17 December 2007 (UTC)

[edit] Non-optical mirrors.

0. The subsection about non-optical mirrors should be added.
There exist acoustic mirrors and atomic mirrors. They should be mentioned.
1. As for X-ray mirrors and the picture of the explosion due to reflection of X-rays, it looks as a confusion rather than a way of fusion. The subseciton about reflection of X-rays in the nuclear bomb is not supported by literature. The same should be addressed to the article Nuclear_weapons_design which uses the same picture without to justify it. Even worse: references

indicate that the efficient reflerction of X-rays is possible only at the grazing incidence, with the grazing angle of order of 10-6 radian. The figure indicates the revlection at angle of order of 45 degrees, this looks as either a joke or an error; it is 6 orders of magnitude out of reality. X-rays reflected from a solid angle 10-12 steradian should not have any implosive effect.
2. Let us remove the doubtful figure and provide links to other wiki-articles about reflection of invisible waves. dima (talk) 22:45, 7 April 2008 (UTC)

[edit] Retroreflector

Retroreflectors include spherical mirrors, of which there exists a very common biological example, the tapetum lucidum of the many animals that display eyeshine. Please add appropriate mention of that to this article. --Una Smith (talk) 03:34, 2 June 2008 (UTC)