If an observer where too stand with a lamp in a room with mirroring walls, what would the observer view in the mirrors.
Ideally one should be able to see infinitely many lamps due to multiple reflections from various walls, the floor and the ceiling, arranged into an optical illusion of a cubic lattice. However, each reflection appears to be more distant than the previous one, so eventually they become too small to discern. Moreover in reality mirrors are not perfect, some light is absorbed, some scattered, so after a finite number of reflections there is no light left to reflect further. As a result, only finite number (albeit possibly large) of reflections is visible.