Translation and rotation of plane mirrors

A translation of a plane mirror of perpendicular vector yields an image translation of vector .

A rotation of a plane mirror M1 with an angle θ around any axis parrallel to M1 yields a mirror plane M2 which cuts through M1 following a line D parrallel to the rotation axis.

The image of an object in M2 is obtained from the image in M1 by a rotation of axis D and angle 2θ.

This is true for a luminous ray or for a rays beam.