What must be used in the construction of waveguides?

Waveguides are structures used to guide electromagnetic waves, particularly in the microwave frequency range. The fundamental requirement for a waveguide is that it must be constructed from conductive material. This is because the walls of the waveguide must reflect the electromagnetic waves effectively, ensuring they travel through the guide without significant loss.

Conductive materials, typically metals like copper or aluminum, provide the necessary properties to contain and direct the electromagnetic waves by allowing them to propagate through the guide’s interior while reflecting off the walls. The conductivity of the material facilitates the necessary boundary conditions for wave propagation, which is essential for the proper functioning of any waveguide.

Other material options mentioned, such as plastics, insulating materials, or glass, do not possess the conductivity needed for effective waveguiding. Instead, they may serve different purposes in engineering and electronics but are not suitable for maintaining the electromagnetic properties required in waveguides.