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Q & A: Catching Light

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Most recent answer: 10/22/2007
Q:
Suppose you have a hollow box. The inside surface is made of mirror. One of the faces of the box is hinged so it can be opened and closed. If you shine a light inside it, and then close the lid, will there still be light inside???! The mirrors should be reflecting the light off each other and keep it in the box forever... shouldn’t they?
- Chris
UK
A:
Chris -

Your theory is mostly good, but the problem would be that light is fast. There is absolutely no way that you could close the box and 'catch' the light. And even if you could, you'd have to have perfectly reflective mirrors. Real mirrors can't really reflect all of the light that hits them - it's inevitable that at least a few light waves will get absorbed each time. The same goes for the corners, edges, and seams of the box... If even the tiniest bit of light can be absorbed at any spot, all of the light will be absorbed, since it bounces around in the box so fast.

-Tamara

(published on 10/22/2007)

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