Faraday cages - Size of holes

Question

I wanted to learn more about Faraday cages and one thing that caught my attention is the relationship between the wave frequency and the hole in the cage. Why is that the higher the frequency of the wave the smaller the holes it can penetrate? The frequency is supposed to correlate the number waves and time so how does this all fit together?

Answer 1

The size of any holes need to be significantly smaller than the wavelength of light you want to block.

If you go to high enough frequencies then the wavelength becomes small enough for the waves to diffract through your cage.

If you look at What is the relationship between Faraday cage mesh size and attenuation of cell phone reception signals? you will see that, for a rectangular mesh, the critical thing is that the mesh width should be smaller than $\lambda/2$. Below this, the signal amplitude will be attenuated exponentially, on a length of $\sim \lambda/2\pi$, so ideally your mesh would be thicker than this.

Answer 2

microwave ovens work at a wavelength of about 10 cm. If you measure the hole diameters in the screen that sits in front of the window in the door of the oven, you'll have your answer.