Two way mirror

two way mirror

What is a two way mirror?

two way mirror

A two way mirror usually is a quarter inch of glass, a 1 micron layer of silver and then a quarter inch of dark glass.

Looking from the clear glass side, the reflection looks normal but maybe a little bit dark. If on the other side of the two way mirror is a dark room, very little light gets through the dark glass and the silver from the dark room. People outside will not notice anything other than the bright reflection from their side.

In the darkened room, little is reflected because light would have to go through two layers of dark glass. However, light from the outside bright room comes through the thin silver and one layer of dark glass and those in the darkened room can see out.

How do two-way mirrors work?

Typically, mirrors are composed of a piece of glass covering a layer of metal (usually aluminium). When light passes through the glass and hits the metal it is reflected, which is why you see yourself when you look into it.

A two-way mirror also contains this metal coating, but much less of it is used. For example, if just half the mirror’s total surface area is covered by reflective molecules, the two-way mirror reflects only half of the light that hits it, meaning the remaining light can pass through to the other side. As long as the room on the other side is darkened, it will be possible to see through the mirror into the brighter room.

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