Plane electromagnetic wave and metallic waveguide

[patjk]

Explain why a plane electromagnetic wave cannot propagate through a metallic waveguide.

I've tried to come up with an answer, but I haven't been able to. I thought metallic waveguides were good since they reflected the propagating wave very well, allowing the wave to move without much loss in power. Am I wrong? Why can't an EM wave propagate through a metallic waveguide?

Many thanks!

 

[gabbagabbahey]

The keyword is plane

 

[patjk]

I understand a plane wave doesn't bounce off the sides of the waveguide. But can't it still propagate down a metallic waveguide, nonetheless?

Cheers!

 

[patjk]

In addition to the question above, what significance would an antenna traveling across water have on the wave? would the water absorb some of the wave instead of reflecting it, causing the signal to weaken?

Cheers!

 

[paranormal]

I can provide an explanation for why a plane electromagnetic wave cannot propagate through a metallic waveguide.

First, let's define what a plane electromagnetic wave and a metallic waveguide are. A plane electromagnetic wave is a type of electromagnetic radiation that travels in a straight line and oscillates perpendicular to the direction of propagation. It does not require a medium to propagate and can travel through a vacuum. On the other hand, a metallic waveguide is a structure made of metal that is used to guide and confine electromagnetic waves, typically in the radio frequency range.

Now, the reason why a plane electromagnetic wave cannot propagate through a metallic waveguide is due to the waveguide's physical properties and structure. A metallic waveguide is designed to contain and guide electromagnetic waves by reflecting them off its walls. The walls of a metallic waveguide are usually made of a highly conductive material, such as copper or aluminum, which have a high electrical conductivity. When an electromagnetic wave encounters these walls, it induces an electric current on the surface of the walls, which in turn generates a magnetic field. This magnetic field then interacts with the electric field of the wave, causing it to reflect back and forth within the waveguide.

Now, a plane electromagnetic wave has a specific wavelength, which is determined by its frequency and speed of propagation. In order for the wave to propagate through a waveguide, its wavelength must be smaller than the dimensions of the waveguide. This is because the wave must be able to reflect off the walls of the waveguide in order to be guided. However, the wavelength of a plane electromagnetic wave is typically much larger than the dimensions of a metallic waveguide, making it unable to fit within the waveguide and be guided.

In addition, the highly conductive walls of a metallic waveguide also act as a barrier for the electric and magnetic fields of the plane electromagnetic wave. These fields cannot penetrate through the walls and therefore cannot propagate through the waveguide.

In conclusion, a plane electromagnetic wave cannot propagate through a metallic waveguide due to its physical properties and structure. The wave's wavelength is too large to fit within the dimensions of the waveguide, and the highly conductive walls act as a barrier for the wave's electric and magnetic fields.