Long Path Diffraction illustrates the wave nature of light by letting visitors see the interference patterns caused when light bends around an object. Normally, these patterns are too small to see. In this exhibit, a laser light zigzags inside until it spreads out on a screen at the front of the exhibit. Because laser light is monochromatic (one color) and coherent (all the light waves travel together), the interference patterns are very clear. Visitors can hold various objects in the path of the laser light and see their shadows on the screen. The dark and light bands around the edges of the shadows are the interference patterns.