Speaker 1: Welcome to brain stuff from how stuff works. Hey, brain stuff.
Speaker 1: This is Christian Sager. There is no denying it. Microwave
Speaker 1: ovens are super convenient. They can heat food much more
Speaker 1: quickly than a conventional oven, although not always with the
Speaker 1: same results. And there's an entire industry of food made
Speaker 1: specifically for these nifty gadgets. But how do they work? Yeah,
Speaker 1: of course you're saying right now, well microwaves. Sure, yeah, microwaves.
Speaker 1: But what the heck are microwaves? Good question, Christian. Microwaves
Speaker 1: are a type of wave on the electro magnetic spectrum,
Speaker 1: and their sandwiched between radio waves and infrared radiation. In
Speaker 1: the case of microwave ovens, the most common wave frequency
Speaker 1: is roughly two thousand, four hundred and fifty mega hurts.
Speaker 1: That's about two point four or five giga hurts. Waves
Speaker 1: in this frequency range have an interesting property. They're absorbed
Speaker 1: by water, fats, and sugars, and once absorbed, they're converted
Speaker 1: directly into atomic motion, which we like to use as heat.
Speaker 1: These waves have another convenient property. They're not absorbed by
Speaker 1: most plastics, glass, or ceramics. Metal, however, does reflect microwaves,
Speaker 1: which is why it's a bad idea to leave a
Speaker 1: spoon and you cheese dip when the oven's on. It's
Speaker 1: also why the devices have metal walls for reflection. You'll
Speaker 1: often hear people say microwave ovens cook from the inside out, right,
Speaker 1: that's the key to the speed. Think about it like this.
Speaker 1: Let's say you're baking a cake in a conventional oven.
Speaker 1: Normally you would bake it at three and fifty degrees
Speaker 1: fahrenheit or a hundred and seventy seven degrees celsius. But
Speaker 1: this time you accidentally set the oven at six hundred
Speaker 1: degrees fahrenheit. The outside of the cake will burn before
Speaker 1: the inside even gets warm, and you'll have ruined somebody's birthday.
Speaker 1: In a conventional oven, the heat has to grate by
Speaker 1: conduction from the outside of the food toward the middle. Hot,
Speaker 1: dry air on the outside evaporates moisture, so the outside
Speaker 1: can be crispy and brown like the crust unbread while
Speaker 1: the inside is moist In microwave cooking, the radio waves
Speaker 1: penetrate the food and excite water and fat molecules more
Speaker 1: or less evenly throughout. No heat has to migrate toward
Speaker 1: the interior by conduction. There's heat everywhere all at once
Speaker 1: because the molecules are all excited together. There are limits
Speaker 1: to this, though. Microwaves penetrate unevenly in thick pieces of food.
Speaker 1: They don't make it all the way to the middle,
Speaker 1: and there are also hot spots that are caused by
Speaker 1: wave interference. But you get the idea. The heating process
Speaker 1: is different because you are exciting atoms rather than conducting heat.
Speaker 1: Inside a microwave oven, the air is at room temperature,
Speaker 1: so there's no way to form a crust. That's why
Speaker 1: microwaveable pastries or hot pockets sometimes come with a little
Speaker 1: sleeve made out of foil and cardboard. The sleeve reacts
Speaker 1: to microwave energy by becoming very hot. This exterior heat
Speaker 1: lets the crust become crispy, as it would in a
Speaker 1: conventional oven. Check out the brainstuff channel on YouTube, and
Speaker 1: for more on this and thousands of other topics, visit
Speaker 1: how stuff works dot com.