Meditating on Reflected Light
Most recent answer: 02/18/2015
- Jason G. (age 19)
Ithaca, NY, USA
Here's a guess. Those reflectors are designed to reflect a significant fraction of light back the direction it came from. The reason is obvious- you want someone driving a car, which has lights, to be able to see you easily. So if you put your face in a light spot, from which light is going out all directions, including toward the reflector, you'd expect to see more light coming back from the reflector than if you put your face in a less lit spot.
I just tried the experiment with a bike reflector and sunlight streaming in the window. The reflector definitely has an extra-strong reflection back toward the light source. In fact, it's a little hard to type this because I got that reflection right in my eye. There wasn't enough reflection off my sun-lit face, however, to show up much when looking at the reflector. Perhaps in your case there was something much more reflective in the same lit-up region where you put your face.
The way you can make a reflector that preferentially reflects straight back is by using little 3-sided regions meeting at right angles in a corner. Light bouncing off the 3 sides reverses directions along each of the three axes, so it ends up making a complete turn-around.
By the way, you may be interested in this true anecdote about someone else who got distracted during class.
(published on 02/18/2015)