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Q & A: room of perfect mirrors

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Most recent answer: 06/23/2013
Q:
If you had a room where the walls ceiling and floor were all made of impossibly efficient mirrors and there was nothing in the room what would you see looking in the mirrors? (when I say there is nothing in the room I do not mean there is no light)
- Alan James Waller (age 17)
Canada
A:

Once you start to look, the room will no longer be completely surrounded by perfect mirrors. It will need a little hole leading to your eye, which absorbs light that hits it as the first stage of sending a signal to your brain. For the sake of argument, let's say that you had a small hole (2mm diameter) and otherwise perfect mirrors around a very large room (10mx10mx10m). Then it could take something like a second for the light in the room to drain away to your eye, enough time to get a clear visual image.

Probably before the little hole was opened, the light bouncing around inside would end up spread all over the place and heading all directions. So you'd see a uniform blur of whatever intensity and color the light happened to have.

After a few seconds, when almost all the original light had been absorbed by your eye, what would be left is a glow of infrared light, the thermal equilibrium spectrum at the temperature of your eye, about 310K. Of course, your eye isn't sensitive to that, since if it were it would always just be seeing its own glow.

Mike W.


(published on 06/23/2013)

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