FTR #60: Be Illuminated; Use Reflectivity1

  1. For science nerds: Reflectivity or reflectance is the fraction of incident electromagnetic power that is reflected at an interface, in contrast to the reflection coefficient, which is the ratio of the reflected to incident electric field. For safety nerds: Retroreflection occurs when surfaces return a portion of the directed light to its source. This is why retroreflective materials appear brightest to observers located near the light source – a driver and the vehicle headlights, for example. This is true for drivers at almost any viewing angle, which makes retroreflective surfaces excellent for night visibility. Source: 3M - Reflectivity (PDF) []