Do you know how to determine if a mirror is 2-way or not? A policewoman who travels all over the US and gives seminars and techniques for businesswomen passed this on. When we visit toilets, bathrooms, hotel rooms, changing rooms, etc., how many of you know for sure that the seemingly ordinary mirror hanging on the wall is a real mirror, or actually a 2-way mirror (I.e., they can see you, but you can't see them)? There have been many cases of people installing 2-way mirrors in female changing rooms. It is very difficult to positively identify the surface by just looking at it. So, how do we determine with any amount of certainty what type of mirror we are looking at? Just conduct this simple test: Place the tip of your fingernail against the reflective surface and if there is a GAP between your fingernail and the image of the nail, then it is a GENUINE mirror. However, if your fingernail DIRECTLY TOUCHES the image of your nail, then BEWARE, FOR IT IS a 2-WAY MIRROR! "No Space, Leave the Place." So remember, every time you see a mirror, do the "fingernail test." It doesn't cost you anything. Remember: "No Space, Leave the Place"

if you turn off the light a two-way mirror is more like a window. When I was little I went in for mental testing and a large mirror was next to me. The psychologist said it was so he could see more of my reactions. However I noticed that the mirror, where shadowed looked different and during his questioning I got up and turned the light off. I saw two more psychologists and my mother sitting on the other side of the glass. I waved at her and she waved back. The psychologist got angry with me for bieng so observant. As a result, I was diagnosed with attention deficit disorder lol.

Mirrors in peculiar places tend to be 2 way mirrors. If you go to a timeshare presentation or some other high pressure sales presentation where there is a mirror in the room, chances are that the salesman's supervisor is watching from the other side. Sometimes if you look carefully and/or look from a low enough vantage point, its likely that you will see the ceiling light from the other room.

The snopes article to which others have linked has the answer: http://www.snopes.com/crime/warnings/mirror.asp According to the folks in Mirropane's technical support group, you can use these factors to your advantage by pressing your eyes up against the mirror and cupping your hands around them (to block out the light from the room you're in): if you're truly dealing with a transparent mirror, you should be able to see at least a little something of the open area behind it. Also, rapping on the mirror should provide an aural clue: ordinary mirrors have backings and are usually placed against walls, so rapping on them will generally produce dull thuds; transparent mirrors and set into walls with open areas behind them, so rapping on them should produce much more open, hollow sounds.

I would like to point out a slight discrepancy in your "two-way mirror" article. The fingernail test might work for Mirrorpane (TM) mirrors (which have the reflective material on the "front" of the glass), but many two-way mirrors are made exactly like regular mirrors, except that they have either been only lightly coated with a reflective metal BACKING (paint) or the metal backing has small (extremely small) holes in it. The light from a bright room reflecting off the shiny metal back is bright enough that the holes cannot be seen. BUT the reflective metal paint is in the exact same place as it would be on a regular mirror. Therefore, there would still be a gap between the fingernail and its reflection. A better way to determine if it is a two-way mirror is to either turn the light off or dim it, then put your head as close to the glass as possible and to one side. This MAY enable you to see either the holes or if you straight into the mirror up close with no light reflecting off it, you might be able to see the dim room on the other side. Another point is that two-way mirrors are almost invariably FIXED to the wall, so if the one you're looking at is merely hung and there is a wall behind it, then it wouldn't be a two-way mirror, probably. Obviously on ones like the one in my personal bathroom, where the mirror is framed and the back is covered with Kraft paper (just like a good framed picture), there is the possibility of a wireless camera that can see through the backing and transmit the image to a receiver elsewhere. You learn a lot from cops during a 20-year journalism career :-) Sincerely, George Wilhite, Author The Texas Rodeo Murder http://texasrodeo.go.to

A one-way mirror reflects some percentage of the light and lets some other percentage pass. It is a sheet of glass coated with a layer of metal only a few dozen atoms thick, allowing some of the light through the surface (from both sides). It is used between a dark room and a brightly lit room. Persons on the brightly lit side see their own reflection - it looks like a normal mirror. Persons on the dark side see through it - it looks like a transparent window. It may be used to observe criminal suspects or customers (to watch out for theft). The same type of mirror, when used in an optical instrument, is called a half-silvered mirror or beam splitter. Its purpose is to split a beam of light so that half passes straight through, while the other half is reflected — this is useful for interferometry. 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 (ones that do not need external energy); if such a device were 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. (There is no prohibition against one-way windows, however.[1][2] Optical isolators are one-way devices, that are commonly used with lasers.) http://en.wikipedia.org/wiki/Mirror