Microwaves aren't actually full Faraday cages (perhaps some are, but not the ones I've seen): the door seal forms a quarter-wave trap, which is a short circuit

Microwaves aren't actually full Faraday cages (perhaps some are, but not the ones I've seen): the door seal forms a quarter-wave trap, which is a short circuit at the oven's operating frequency, but not at other frequencies.