Waveguide

First, microwaves are guided with almost no loss by a flexible waveguide.

The second part demonstrates the existence of a minimum waveguide size at which waves can still propagate through it.

In the second part, the waveguide is realized by a pair of metal plates that can be brought together to any distance. The microwave source emits microwaves at a frequency of 9.4 GHz. For this frequency, the smallest waveguide size that still supports the fundamental mode comes out to be 1.6 cm (according to the relation $b = \frac{c}{2f}$, where $b$ is the waveguide size and $c$ is the speed of light).

Microwave source and probe detecting the electric field, whose presence (and magnitude) is shown on the voltmeter.

Flexible waveguide conducting waves directly from the source to the probe.

Adjustable waveguide construction. With one metal plate, the field at its edge is nearly zero.

By adding the second plate, we create a waveguide and the field at its end is strong.

Side view of the plate waveguide.

When the waveguide width is greater than 1.6 cm, waves propagate through it.

When the waveguide width is less than 1.6 cm, waves are exponentially attenuated.

Internal: Attachment of metal plates using printed holders.