# Light/physics (?) problem

Discussion in 'Off Topic' started by Seba, Apr 2, 2010.

1. ### aaSebaＤＲ． ＢＩＧ ＦＵＣＫＥＲ， ＰＨＤ

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Imagine you have six square panels of one-way (or two-way, point is you can see through one side, and the other one is reflective) glass. You put those panels into a cube, reflective side in. Now you shine a light into that cube, and take it into a dark room. What happens? Does the cube glow with the light, since it keeps bouncing off the inside mirrors? Or does the cube stay black, because no light can escape?

This has bothered me since I first learned about one-way glass, and it's pissing me off to this day. Answers and speculations are welcome (until I bring my sorry ass to a...wherever one-way glass is sold and do this IRL).

2. ### aaPenguinClinically Diagnosed with Small Mapper's Syndrome

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Build one yourself and find out.

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3. ### GuyovickL1: Registered

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The reflectance of 1 way glass isn't 100%. If it was then you wouldn't be able to see what was on the mirror side of the glass from the clear side. The trick is that more light is being reflected from the mirror side than is passing through from the clear side. If you turned out all the lights on the mirror side you could see through to the clear side.

The light would pass through the mirror side (instead of reflecting forever) and gradually (read: quickly) escape the box. The bottom line is that you could not trap the light indefinitely.

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4. ### aaMick-a-nator

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This is basically a kind of explanation of 2-way mirrors and adds a bit towhat Guyovick said. A 2-way mirror (this is what I think you mean btw) works in either direction, aka both sides can act as a mirror. Which side is reflective depends on which side is lighter. the side with more light on it will reflect some of that light back (looks like a mirror) but the other side will receive some of this light (looks like ordinary glass).
In short, some light will escape into the darker area, then in real life this would be absorbed into the walls of the room.
If though you took an imaginary room with walls that reflect ALL light completely then, if you could put the box into the room faster than light escaped it, the light would be trapped in the room! Brilliant things happen when you create a universe in your head

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So. light speed is 300.000 km/sec. When you would have super reflective mirrors that only absorb one millionth of the energy, and a room of 10x10x10 meter.. all light energy would be practically gone after a matter of seconds.

If you really wanna know how long it takes I could calculate for you..

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6. ### aaYMLVL100 YM

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You know how they work right? As the others said (bar GLaDOS and the rather unhelpful penguin) one side is bright and the other side is dark, so that the bright side sees it's reflection much brighter than the light coming through from the other side. Then of course the dark side can't see it's dark reflection over the bright light coming through the other side.
The important thing here is it's transparent BOTH ways, there is no way to make it so light can only go though one way and is reflected perfectly if it tries to get the other way.

So... the situation you've posed is impossible because these interrogation room mirrors have no 'reflective' side. Each side is equally reflective.

So.... if you set it up ignoring the last statement, you'd see the room lit up as though you were shining a light through a normal glass cube, well, maybe slightly darker depending how thick your reflective layer is.

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7. ### aaA Boojum SnarkToraipoddodezain Mazahabado

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and, under the purely theoretical assumption you do have a material that is 100% reflective on one side and 100% transparent on the other. Your cube would appear black, because no light can come out of it, and no light can bounce off the outside.

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8. ### aaYMLVL100 YM

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More interesting to note, the cube would always appear black no matter what the conditions outside.

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9. ### aaSebaＤＲ． ＢＩＧ ＦＵＣＫＥＲ， ＰＨＤ

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Interesting... Shame that theoretical assumptions are only theoretical assumptions

Thanks for everyone, just for the hell of it.