What are hollow metal tubes used to transfer energy from one point to another called?

Hollow metal tubes used to transfer energy from one point to another are known as waveguides. Waveguides are specifically designed to direct electromagnetic waves, particularly in the microwave frequency range, by constraining the waves in a manner that maximizes their efficiency. The physical structure, typically rectangular or circular in shape, allows for the effective transmission of the energy without significant loss, which is crucial for maintaining signal integrity in advanced communication systems.

In contrast, transmission lines generally refer to structures that are used to transmit electrical signals, but they can include a variety of forms such as coaxial cables and twisted pairs, not just hollow metal tubes. Fiber optics involves the use of thin strands of glass or plastic to transmit data as light rather than electromagnetic waves, making it a different medium entirely. Conductors are general materials that facilitate the flow of electric current, encompassing a broad range of materials, but they do not inherently convey the structural and waveform-specific qualities of waveguides. This detailed understanding reinforces why the term "waveguides" is accurate in this context.