If you can see an object, it is technically reflective since it is bouncing light to your eyes. For a surface to be reflective, it simply has to throw or bounce back light from its surface without absorbing all of it. Most objects use scattered or diffused reflectivity where light is scattered everywhere. A mirror would be a good example of a specular reflective surface. Retro reflective surfaces are reflective like a mirror, but with one added characteristic. These surfaces return light back to the source of the light and no where else. Reflective tape or reflective road markers are examples of this. I talk about mirror reflectivity and retro reflectivity in another article. But in summary, they are two completely different types of reflectivity, with completely different applications. A stop sign and the mirror on your bathroom wall operate by bouncing light, but they are obviously very different.
So if you shine a light on a reflective surface like a mirror, the light will bounce and leave the surface at a different angle. This is because mirrors are designed with a completely flat reflective surface that does not distort light. By shining a light on a mirror in your home you can easily test this phenomenon. You can also note that you can see yourself in a mirror, whereas you cannot see yourself when you look at a piece of reflective sheeting. So although both reflect light, they are very different.
If you shine the same light on a retro reflective surface, the light returns only back to the source of the light. If you shine multiple lights at a mirror, the beams will bounce to multiple other locations. The retro reflective surface will return each beam of light back to the source of the light. So a mirror redirects light, and a retro reflective surface returns light.
The simple explanation for how retro reflective surfaces work is that they bend light in such a way that it always exits the surface the way it came in, which is back to the light source. The diagram above shows how this works for reflective prismatic surfaces. Man made prisms bend and bounce the light so that it is directed back to the source. These man made cubes are a part of brighter reflective tape, and all road markers. The image below shows a glass bead reflecting in the same way. Glass bead reflective surfaces are bright, but not as bright as prismatic surfaces. Light enters the microscopic sphere, is bent, and then exits the way it came. This is similar to prisms but less efficient.
So in summary, both a mirror and a sheet of reflective tape are reflective, but only the tape is retro reflective. A disco ball and a road marker are both reflective, however, only the road marker is retro reflective. So they are similar, but distinctly different. Our article on the different better mirrors and reflective tape goes into more detail about this phenomenon.
Steven Cole (Economics, MBA – University of West Florida , Business & Innovation – Stanford University) 25 years of experience in the reflective safety business. Specializing in vehicle accident and rear end collision reduction through increased visibility.