Waveguide

Structure that guides waves efficiently

A waveguide is a structure that guides waves by restricting the direction of transmission of energy. Common types of waveguides include acoustic waveguides which direct sound, optical waveguides which direct light, and radio-frequency waveguides which direct electromagnetic waves other than visible, or near visible, light, like radio waves. Without the physical constraint of a waveguide, waves would expand into three-dimensional space and their intensities would decrease according to the inverse square law.

From Wikipedia, under CC BY-SA. More on occurri.