Two parallel plane mirrors are separated by distance d. For a sequence generated by alternating reflections, what is the separation between successive images lying behind the same mirror?
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Two parallel plane mirrors are separated by distance d. For a sequence generated by alternating reflections, what is the separation between successive images lying behind the same mirror?

G1 Physics · Accepted Answer

Every two reflections translate the corresponding image position by 2d. Hence successive members of the same image family behind one mirror are separated by 2d.