Talk:Mirror
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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)
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)
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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)
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)
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)
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] (http://www.arrow-dynamics.com/hardness.htm)) 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)
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
"right-reading" mirror
Cecil Adams in an old Straight Dope column ([2] (http://www.straightdope.com/classics/a2_082.html)) 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 (http://www.truemirror.com/) 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)
Applications - Image
Francescadani_mirror.jpg
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 visit the site linked on the picture, I think this image needs to go. --Morbid-o 15:48, 20 Jun 2005 (UTC)