An observer located between two flat mirrors forming a particular dihedral angle will see two contiguous partial images of his face, with a single eye: a "cyclops image". An explanation on the formation of this picture is presented, based on geometric constructions, along with a simple experimental proposal, allowing its approach in high school and trying to renew the interest in the problem of the association of flat mirrors, which seems to be settled in textbooks, and leads to some uncritical discussions.
optics; mirror; reflection
