Each glass bead works as follows : An incoming light beam refracts
as it passes through the front surface of the glass bead and reflects
off a mirrored surface behind the bead.
The beam then passes back through the front surface, is refracted
as it leaves the bead, and returns toward the light sources.
2) Cube corner reflection (Micro-prism type : Reflective PVC sheet)
Cube corners are retro-reflective lens elements like glass beads. Each cube corner
has three mutually perpendicular refractive surfaces. An incidental
light ray is refracted on each of the three surfaces and is returned
to its source parallel to its initial direction. It functions
like a ball bounced into the corner of a room.
