Hey Guys.
I am new here but I really have curiosity about how one way mirrors work.
I mean you see them on CSI and all that, when the criminal is in this room and those Crime "Doods" look at them through the mirror which on their side is a window.The criminal can just see a mirror.
I just want to know how do these things work.
Hi Dood,
Yes, interesting watching films with crime scenes I guess.
What it is, is that a one-way mirror has a reflective coating applied in a very thin, sparse layer - so thin that it's called a half-silvered surface.
This name, half-silvered comes from the fact that the reflective molecules coat the glass so sparsely that only about half the molecules needed to make the glass an opaque mirror are applied.
At the molecular level, there are reflective molecules speckled all over the glass in an even film but only half of the glass is covered. The half-silvered surface will reflect about half the light that strikes its surface, while letting the other half go straight through. It turns out that half-silvered mirrors are also essential to many types of lasers.
So why doesn't the "criminal suspect" see the detectives in the next room?
Its due to the lighting of the two rooms.
The room in which the glass looks like a mirror is kept very brightly lit, so that there is plenty of light to reflect back from the mirror's surface. The other room, in which the glass looks like a window, is kept dark, so there is very little light to transmit through the glass. On the criminal's side, the criminal sees his own reflection. On the detectives' side, the large amount of light coming from the criminal's side is what they see. In many ways, it's the same as if people were whispering in one room while a loud stereo played in the other. The sound of the whisper might carry into the room with the stereo, but it would be drowned out by the intensity of the music.
If the lights in the room with the mirror are suddenly turned out, or the lights in the observation room suddenly turned on, then the one-way mirror becomes a window, with people in each room able to see those in the other. You can see this effect in any mirrored office building at night... if the light is on in an office, you can see into the office just fine.
Here are some useful links:
How light works
How lasers workOne way mirrors
Hope it helps!
Yes, interesting watching films with crime scenes I guess.
What it is, is that a one-way mirror has a reflective coating applied in a very thin, sparse layer - so thin that it's called a half-silvered surface.
This name, half-silvered comes from the fact that the reflective molecules coat the glass so sparsely that only about half the molecules needed to make the glass an opaque mirror are applied.
At the molecular level, there are reflective molecules speckled all over the glass in an even film but only half of the glass is covered. The half-silvered surface will reflect about half the light that strikes its surface, while letting the other half go straight through. It turns out that half-silvered mirrors are also essential to many types of lasers.
So why doesn't the "criminal suspect" see the detectives in the next room?
Its due to the lighting of the two rooms.
The room in which the glass looks like a mirror is kept very brightly lit, so that there is plenty of light to reflect back from the mirror's surface. The other room, in which the glass looks like a window, is kept dark, so there is very little light to transmit through the glass. On the criminal's side, the criminal sees his own reflection. On the detectives' side, the large amount of light coming from the criminal's side is what they see. In many ways, it's the same as if people were whispering in one room while a loud stereo played in the other. The sound of the whisper might carry into the room with the stereo, but it would be drowned out by the intensity of the music.
If the lights in the room with the mirror are suddenly turned out, or the lights in the observation room suddenly turned on, then the one-way mirror becomes a window, with people in each room able to see those in the other. You can see this effect in any mirrored office building at night... if the light is on in an office, you can see into the office just fine.
Here are some useful links:
How light works
How lasers workOne way mirrors
Hope it helps!
Hi Dood,
It is only a very thin coating of silvering on the mirror. This is actually partially transparent. The truth is we see things on the other side of these mirrors depending on the level of ambient lighting on either side of the glass. On the criminals side of the glass the ambient light level is high so what the criminals see is "mainly" the reflection from within his room. In the other side the interior light level is low so the light from the other side is high... you can see through it. The general principle was also the basis of an old optical illusion used in magic shows in the early days. Check this out ...
Wikipedia: Pepper's Ghost
It is only a very thin coating of silvering on the mirror. This is actually partially transparent. The truth is we see things on the other side of these mirrors depending on the level of ambient lighting on either side of the glass. On the criminals side of the glass the ambient light level is high so what the criminals see is "mainly" the reflection from within his room. In the other side the interior light level is low so the light from the other side is high... you can see through it. The general principle was also the basis of an old optical illusion used in magic shows in the early days. Check this out ...
Wikipedia: Pepper's Ghost
Thanks Guys 