the heating chamber. This I accept. What I struggle with is, how is the microwave casing itself (which is made entirely of metal), be safe, when a metal dish or tinfoil tray, would not ?
Answers (1)
You are asking for a brief explanation of microwave theory, and that is not a brief subject.
Popcorn is not popped by microwaves, the bag contains a metal plate which gets hot and melts the shortening and fries the popcorn just as if you had it in a skillet on the stove. It took some experimentation to find just the right way to put a metal plate in a paper bag in a microwave oven to pop corn without burning the bag or exploding the microwave generator.
So you see, maybe metal is dangerous, and maybe it's not. It took many years to learn a few things about microwaves.