Mrs. tracer is worried about my health. When I prepare small cups of liquid in our microwave oven, I watch them like a hawk (through the Faraday-cage-protected glass window in the oven door) to make sure they don’t boil over. Mrs. tracer doesn’t want me to do this because, she contends, the microwave radiation that leaks through the Faraday cage and the door seals can damage my retinas if I’m looking directly into it.
Is there any truth to this notion? Any cases of retinal damaged from prolonged microwave ogling? Personally, I’d think that if there was enough microwave energy escaping from my oven to damage my retinae, it wouldn’t matter whether I was looking straight into it or looking away (what with the lenses of my eyes being optimal for focusing visible light on my retinae, not high-frequency radio).
If the grid is undamaged, it is physically impossible for microwave radiation to leak through it, as the holes are smaller than the wavelength of the radiation. If the seal is damaged, stuff can leak out around the sides.
Minor nitpick: The door isn’t a Faraday cage. A Faraday cage is a metal box, which, as Michael Faraday discovered, metal boxes prevent radio waves inside the box from getting to the outside, and also prevents radio waves from outside the box from geting into the inside. As long as the door is closed, the area where you cook the food in is effectively surrounded by a Faraday cage consisting of the metal walls of the box plus the door. The door itself is just a piece of metal with holes in it.
As Smeghead said, the trick with the microwave door is that the holes are smaller than the wavelength of the radio waves. As far as the radio waves are concerned, the door is pretty much the equivalent of a solid piece of metal. This is also why commercially sold Faraday cages are made out of metal screen and aren’t solid metal boxes. The screen works just as well as solid metal, and is lighter, cheaper, and lets air through.
Also, it’s my understanding that the two areas of your body most easily damaged are your eyes and your testicles. Since your eyes are directly in front of the door (and hence are shielded by it), and the most likely place for your microwave to develop a leak is around the seals, your testicles are far more likely to suffer damage than your retinas.
I’m sure Mrs. tracer will find that comforting to know.