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Do two mirrors facing each other produce infinite reflections?

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While they seem to extend into the infinite, the truth is a little darker.

Asked by: Sal Smythers, Cambridge

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It’s always fun to look at the multiple reflections formed by opposing mirrors in lifts, washrooms and the like. But while they seem to extend into the infinite, in reality they get progressively darker and fade into invisibility long before they get there. That’s because mirrors absorb a small fraction of the energy of the light striking them each time. Thus even the best mirrors are unlikely to generate more than a few hundred visible reflections.

Why do mirrors reverse left and right, not up and down? © iStock

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Authors

Robert is a science writer and visiting professor of science at Aston University.

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