Holography uses light to create what seems like a three-dimensional image of an object. You often find some wonderful examples at art exhibitions and museums.

Holography takes advantage of the diffraction and interference of light. There are several ways to create holograms, but the most common is using the laser, which generates coherent light. Holograms are created by dividing a laser beam in two using a beam splitter, illuminating an object with one of the divided beams, and simultaneously illuminating a dry photographic plate with the light reflected from the object (diffracted light) and the light from the second divided beam (reference light) at an angle. The diffracted and reference light interfere with one another to make an interference pattern.

The recorded pattern is the hologram. When the hologram is illuminated using a laser at the same angle as the reference light, the pattern diffracts the laser light, reproducing the image. As shown in the image below, some kinds of hologram reproduce the actual image and the virtual image.