D: Today's moment of science is inspired by the plethora of crime dramas on television these days. I will unveil the magic behind one-way glass.
Link to Northglass
Y: I've always wondered how that works.
D: The trick is simpler than you might think. Most mirrors are made by applying a thin layer of a reflective material, aluminum in most cases, to the back of a sheet of glass. This is called back silvering, and it makes the glass opaque. When we look in a mirror, our image is reflected by the aluminum, which is made more durable by its glass covering.
Y: So is one-way glass not fully silvered?
D: Exactamundo. The reflective material is applied less densely. This is called half-silvering. The effect is that the glass is not completely opaque like a traditional mirror. About half the light striking the glass passes through it, and the other half is reflected.
Y: Hmm. It seems like people on both sides would see the same thing: fractured images of both themselves and the people on the other side.
D: Now for the second trick to one-way glass: the lighting. The room the suspect is in is kept bright, so that the reflective quality of the glass prevails. The room on the other side of the glass is kept dark, so that instead of their reflections, the detectives see what is illuminated on the suspect's side of the glass: the suspect.
Y: What if the light were to be turned up on the detective's side?
Contact us to discuss your requirements of one way mirror. Our experienced sales team can help you identify the options that best suit your needs.
D: Or turned down on the suspect's side? The magic would fizzle, and glass would become a window for both parties.A one-way mirror, also called two-way mirror[1] (or one-way glass, half-silvered mirror, and semi-transparent mirror), is a reciprocal mirror that appears reflective from one side and transparent from the other. The perception of one-way transmission is achieved when one side of the mirror is brightly lit and the other side is dark. This allows viewing from the darkened side but not vice versa.
The first U.S. patent for a one-way mirror appeared in , then named a "transparent mirror".[2][3]
The glass is coated with, or has been encased within, a thin and almost transparent layer of metal (window film usually containing aluminium). The result is a mirrored surface that reflects some light and is penetrated by the rest. Light always passes equally in both directions. However, when one side is brightly lit and the other kept dark, the darker side becomes difficult to see from the brightly lit side because it is masked by the much brighter reflection of the lit side.[4]
A one-way mirror is typically used as an apparently normal mirror in a brightly lit room, with a much darker room on the other side. People on the brightly lit side see their own reflection&#;it looks like a normal mirror. People on the dark side see through it&#;it looks like a transparent window. The light from the bright room reflected from the mirror back into the room itself is much greater than the light transmitted from the dark room, overwhelming the small amount of light transmitted from the dark to the bright room; conversely, the light reflected back into the dark side is overwhelmed by the light transmitted from the bright side. This allows a viewer in the dark side to observe the bright room covertly.
When such mirrors are used for one-way observation, the viewing room is kept dark by a darkened curtain or a double door vestibule. These observation rooms have been used in:
Smaller versions are sometimes used in:
The same type of mirror, when used in an optical instrument, is called a beam splitter and works on the same principle as a pellicle mirror. A partially transparent mirror is also an integral part of the Fabry&#;Pérot interferometer.
For more information, please visit triple glazed glass.