Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, I'm
Speaker 1: Christian Sager. This is brain stuff, and today we're talking
Speaker 1: about one way mirrors a K A two way mirrors
Speaker 1: a K A half silvered mirrors a K. Transparent mirrors
Speaker 1: a K A security mirrors a K. Surveillance mirrors a
Speaker 1: K A observatoor tron's I don't I don't know if
Speaker 1: that last one is a real thing. You know those
Speaker 1: things that you see in crime dramas when one cop
Speaker 1: is interrogating a suspect while another one watches through a
Speaker 1: window that appears from the suspects side to be a mirror.
Speaker 1: That is not magic. TV cops aren't wizards and transparent mirrors.
Speaker 1: They're science. A regular old mirror, the kind hanging over
Speaker 1: your bathroom sink. That's a sheet of glass holding up
Speaker 1: an extremely thin layer of reflective metal, and I mean thin,
Speaker 1: It's less than a micron thin. The metal comes in
Speaker 1: the form of a metall exalt, which can be dissolved
Speaker 1: in liquid and sprayed onto the glass in a process
Speaker 1: called silver ring. That's because silver, in the form of
Speaker 1: silver nitrate, was the first stuff used for this process.
Speaker 1: These days, most mirrors are actually silvered with aluminum, which
Speaker 1: is cheaper and sturdier, and once it dries, the reflective
Speaker 1: layer is given an opaque backing to first of all
Speaker 1: protect it from scratches, and then to stop any light
Speaker 1: that manages to dodge through the metal layer. Without this backing,
Speaker 1: you'd be able to faintly see the wall behind it. See,
Speaker 1: photons are tricky, and mirrors they're not perfect. But what
Speaker 1: if you purposely make a mirror imperfect. Manufacturers of translucent
Speaker 1: mirrors spray and even thinner, more sparse layer of silvering
Speaker 1: onto the glass, meaning it reflects less light. For example,
Speaker 1: let's say half the light of an ordinary mirror, and okay,
Speaker 1: a little light gets absorbed by the silvering, but the
Speaker 1: rest passes straight through the glass like it's a window,
Speaker 1: which it is. A translucent mirror is just a reflective window,
Speaker 1: and it's a window from both sides. Depending on the
Speaker 1: manufacturing process. It might be slightly more reflective from one side,
Speaker 1: but you can look through it from either. So how
Speaker 1: come the suspect sees his reflection but the cop sees
Speaker 1: the suspect. Well, it's just a trick of the light.
Speaker 1: The observer's room is kept dark while the observes room
Speaker 1: is lit up very bright, so on the cop side
Speaker 1: more light is coming through the glass than being reflected
Speaker 1: from the room, and from the suspects side, more light
Speaker 1: is reflecting from the room than being transmitted through the glass.
Speaker 1: And hey, people ask about this a lot. If you
Speaker 1: ever want to testimeror to see if it's translucent, block
Speaker 1: the light around you and try to peer through A
Speaker 1: bright flashlight can help illuminate any thing that might be
Speaker 1: behind that mirror. Check out the brainstuff channel on YouTube,
Speaker 1: and for more on this and thousands of other topics,
Speaker 1: visit how stuff works dot com.