system
Given the following post, respond as if you're commenting on Reddit:
human
Microwaves and radiowaves, how do they penetrate different material?

I was curious at how microwaves dont pass through the metal mesh on the window, I understood this was due to wavelength but it didnt make sense how the waves just can just slide throughthe holes until I read that one should imagine the wavelength doesnt form in one direction but in all like a blob, so the long wavelength disallows it from passing through. That is until I was curious how radiowaves can pass through walls and small bits of earth when they have wavelengths much longer than that of microwaves.

Also how would microwaves penetrate food? Or do they simply heat from the outside?

I did slme reading but nothing seems to click or make sense, is there some kind of sweet spot between wave speed and wavelength?

I havw no background in optics or whatever physics concentration this is, I am simply curious.
gpt
Many materials are nigh useless for attenuating EM radiation. For example, like you say, radio waves will pass through many common obstacles in our world. Likewise, high energy gammas will pass straight through your skin and into your body.

Certain materials, however, such as the mesh on the microwave and also lead, are able to stop electromagnetic radiation. In the case of lead, this is because on the atomic level, the particles of material are very large (lead has a high Z) and it's very easy for the gamma to hit the particles and be absorbed or scattered then absorbed.

In your example, the mesh screen is effective as shielding because the wavelength of a microwave is relatively large. Think about it like trying to feed a rigid S-shaped material through a hole without tilting it or moving it up or down to help it pass through. The holes simply aren't large enough to allow passage, and the waves are reflected. In this way, the microwave acts as a sort of inverse faraday cage for your food.

So you might ask why doesn't visible light also get prevented from leaving the microwave? Visible light has a much smaller wavelength, so it is able to be transmitted through the holes.

EDIT: the reason why radio waves, with an even longer wavelength than microwaves, are able to pass through so many materials anyway is that there are relatively few conductive and or attenuating materials placed around our world, whereas the mesh is both to a degree.