Students investigate multiple reflections.
When you look at your reflection in one mirror, you see light that has come from your face and bounced off the mirror. When there are two mirrors, you see the light that bounces off one mirror, and also the light that bounces from mirror to mirror before coming back to your eyes. The closer the mirrors are together, the more reflections-of-reflections you see.
This is a recommended post-visit activity for a field trip to Science World at TELUS World of Science. It is related to the Kaleidoscope exhibit in Eureka!