Editing Waveguide (section)

=== Radio-frequency waveguides ===
{{Main|Waveguide (radio frequency)|Transmission line}}
Waveguides can be constructed to carry waves over a wide portion of the [[electromagnetic spectrum]], but are especially useful in the [[microwave]] and [[optics|optical]] frequency ranges. Depending on the frequency, they can be constructed from either [[Electrical conduction|conductive]] or [[dielectric]] materials. Waveguides are used for transferring both [[power (physics)|power]] and communication signals.{{sfn|Cronin|1995}}{{rp|1–3}}{{sfn|Okamoto|2010}}{{rp|xiii-xiv}}

[[File:Radar waveguide.JPG|thumb|In this military radar, microwave radiation is transmitted between the source and the reflector by a waveguide. The figure suggests that microwaves leave the box in a circularly symmetric mode (allowing the antenna to rotate), then they are converted to a linear mode, and pass through a flexible stage. Their polarisation is then rotated in a twisted stage and finally they irradiate the parabolic antenna.]]