Retroreflectivity is the property of returning light along the same path
which it was sent, the incedent path
. This action is opposed to sending it off at an opposite angle, like a (flat) mirror
, or scatter
ing it in all directions, like a white
t-shirt. Corner reflector
s and concave spherical mirror
s are both retroreflective. One's reflection
from the first can just have a magnify
ing mirror effect if the spherical nature isn't very pronounced, whereas the second will always look like an exactly reversed mirror image
to the observer.
Sylvanshine and heiligenschein are two common optical illusions caused by the retroreflectivity of droplets of water.