Re: Reflectivity of a wire mesh: Equations?

Paul Ciszek wrote:
In article <%slGi.9120$qV3.3089@trndny02>,
Phil Hobbs <hobbs@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
And btw it isn't obvious that you can't get wavelength dependence from the jellium model--it depends on how your grid is constructed. Long skinny holes in a thick metal won't come out right, but small gaps in a thin metal film will do surprisingly well that way, in the mid IR.

The screen in the window of your microwave oven passes light but blocks
microwaves. Will the jellium model explain this?


Jellium only works in the long wavelength limit. The screen in the microwave is in the long wavelength limit for 12 cm microwaves but not for 500 nm light, so the comparison fails. If you want the difference in the transmission of chicken wire between 100 MHz and 1 GHz, jellium will probably be reasonably good.

There are two main contributions to the transmission physics, namely the boundary reflection (which reduces the field in the apertures) and Kirchhoff diffraction. Jellium captures the first pretty well, and the second can be put in by hand if you need to, using the jellium result for the fields inside the meshes. If the phase delay across the mesh is significant at the scale of your measurement, the long-wavelength approximation is breaking down already.

Cheers,

Phil Hobbs
.