• Question: How do people make 2 way mirrors ?

    Asked by FootballFred03 to Andrew, Jessica on 25 Jun 2015.
    • Photo: Andrew Fensham-Smith

      Andrew Fensham-Smith answered on 25 Jun 2015:


      One way mirrors are actually made by coating glass with a very thin layer of a slightly reflective material (like aluminium). This means that it lets some light through, and reflects some light.

      Now imagine the mirror is separating two rooms – one light and one dark. If you were in the dark room, almost no light would be bouncing onto it, and you would see the light that goes through from the bright room, and not any light on your side. If you were on the bright side, almost no light from the other side is coming through, but lots on your side is bouncing off. That’s how it work – the bright room see’s a mirror, while the dark room can see through. If you switched the lights off in the light room, and switched the lights on in the dark room, then the opposite would happen and the people in the (previously dark, now light) room would see a mirror and the people in the (previously light, now dark) room would see the people in the other room.

      Hope this helps!

    • Photo: Jessica Wade

      Jessica Wade answered on 25 Jun 2015:


      FAB Question Fred!

      Mirrors are super neat because they reflect light, and let us see ourselves or see what’s behind us.

      Andrew’s already explained how it works, but I can tell you some other cool things. I guess the first thing to make clear is that a two-way mirror is actually a one-way mirror (how confusing is that? We physicists like to do things like that. Look up the temperature ‘absolute 0’, it’s not actually 0 degrees C)

      They cover one side of the glass with a special substance that is called ‘micropane’. When you stand next to the treated side you see your reflection, but next to the other side it looks like a tinted window.

      They were first patented (‘claimed’) in 1903 by some nosy Americans. The really neat thing from a physics point of view is that nothing can ever really be a ‘two way mirror’ because light actually always travels the same on both sides. If you watch a police show you’ll see what I mean, the darker room is much harder to see because the reflection is so much from the bright room.

      People use them for spying, or in police stations for interrogation, or for reality TV! Another interesting use is in teleprompters for TV shows- when the journalist or newsreader seems to be reading but staring directly at the camera. There, they project text onto a glass that is right in front of the camera. There’s another awesome use, championed by Snoop Dogg and Dr. Dre at some music festivals. It is a clever stage trick used in lots of haunted houses. Using two way mirrors, you can make ghostly objects fade on and off the stage, or transform some objects to new objects. This trick uses tilted two way mirrors. The oldest description of this was in 1658!

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