Special Conditions: Night or day

Doing the Deed

Counterfeit license plates are used by car thieves. They may look authentic to ordinary people but police know how to detect the fakes. You can too, but you need to look at license plates from a whole new angle. Many license plates have secret images, but it's the viewing angle that reveals them. although different states have different identifying symbols they are almost always placed in a vertical row down the center of the plate.

The secret symbols are invisible unless you view the plate from an angle of 30 degrees. So stand facing the license plate at a distance of four to eight feet. The correct distance for you depends on your height. The taller you are the farther away you'll have to stand.

We easily saw the outline of New York State on our license plates in the daytime. But it was even more dramatic at night when the image was illuminated by a flashlight held near our eyes.

Insider Information

The secret symbols are embedded in the reflective sheeting that covers the plate. The sheeting has a layer of tiny glass beads embedded in clear plastic. Behind the beads is a mirror-like coating. When viewed from most angles, the beads reflect back just about all the light that strikes them.

However, the beads in the pattern of the secret image are treated so that they don't reflect any light when viewed from an angle of 30 degrees. The non-reflecting beads make up the dark areas of the secret pattern.

The reflective sheeting is provided to the states by the 3M Corporation, the only company that makes it. The manufacturing process is so sophisticated that it is unlikely that crooks will be able to duplicate it. Holograms on credit cards serve the same purpose as the secret images on license plates.

From DON'T TRY THIS AT HOME: Science Fun for Kids on the Go, co-authored with Kathy Darling, illustrated by True Kelley. Morrow Junior Books, 1998