All Problems Photometry and Geometrical Optics
Problem 5.14
Demonstrate that a light beam reflected from three mutually perpendicular plane mirrors in succession reverses its direc tion.
5.14. Suppose are the unit vectors of the normals to the planes of the given mirrors, and are the unit vectors of the incident ray and the rays reflected from the first, second, and the third mirror. Then (see the answer to the foregoing problem): Summing termwise the left-hand and right-hand sides of these expressions, it can be readily shown that .