We’ve all heard that it’s not safe to put metal in the microwave. But the fact of the matter is, we often put metals in the microwave—like when we heat up a Hot Pocket, for example. Its pouch has a thin layer of aluminum lining that is designed to absorb the microwaves and heat up a bit to brown the outside of the Hot Pocket.
Plus, the inside walls of your microwave oven are made of metal. This forms a Faraday cage, which traps the microwaves inside the box, so that they cook the food and not things around the microwave oven (like you). The microwave window also has metal mesh lining it. The holes in this mesh are smaller than the wavelengths of the electromagnetic radiation your microwave is producing, which keeps the waves from passing through the holes. Visible light, however, is comprised of much smaller wavelengths, so that form of radiated energy passes through the holes just fine, allowing you to see inside your microwave while it’s running without getting cooked yourself.
via Mental Floss
