1 00:00:02,040 --> 00:00:10,000 Speaker 1: Welcome to brain stuff from how stuff works. Hey, brain stuff. 2 00:00:10,039 --> 00:00:13,040 Speaker 1: This is Christian Sager. There is no denying it. Microwave 3 00:00:13,080 --> 00:00:16,360 Speaker 1: ovens are super convenient. They can heat food much more 4 00:00:16,440 --> 00:00:19,959 Speaker 1: quickly than a conventional oven, although not always with the 5 00:00:19,960 --> 00:00:23,919 Speaker 1: same results. And there's an entire industry of food made 6 00:00:23,920 --> 00:00:29,240 Speaker 1: specifically for these nifty gadgets. But how do they work? Yeah, 7 00:00:29,320 --> 00:00:32,800 Speaker 1: of course you're saying right now, well microwaves. Sure, yeah, microwaves. 8 00:00:32,840 --> 00:00:37,120 Speaker 1: But what the heck are microwaves? Good question, Christian. Microwaves 9 00:00:37,159 --> 00:00:40,599 Speaker 1: are a type of wave on the electro magnetic spectrum, 10 00:00:40,640 --> 00:00:44,800 Speaker 1: and their sandwiched between radio waves and infrared radiation. In 11 00:00:44,840 --> 00:00:48,320 Speaker 1: the case of microwave ovens, the most common wave frequency 12 00:00:48,479 --> 00:00:52,040 Speaker 1: is roughly two thousand, four hundred and fifty mega hurts. 13 00:00:52,040 --> 00:00:55,440 Speaker 1: That's about two point four or five giga hurts. Waves 14 00:00:55,440 --> 00:00:59,200 Speaker 1: in this frequency range have an interesting property. They're absorbed 15 00:00:59,200 --> 00:01:03,160 Speaker 1: by water, fats, and sugars, and once absorbed, they're converted 16 00:01:03,200 --> 00:01:07,720 Speaker 1: directly into atomic motion, which we like to use as heat. 17 00:01:08,240 --> 00:01:12,240 Speaker 1: These waves have another convenient property. They're not absorbed by 18 00:01:12,280 --> 00:01:17,800 Speaker 1: most plastics, glass, or ceramics. Metal, however, does reflect microwaves, 19 00:01:17,840 --> 00:01:20,080 Speaker 1: which is why it's a bad idea to leave a 20 00:01:20,120 --> 00:01:22,800 Speaker 1: spoon and you cheese dip when the oven's on. It's 21 00:01:22,920 --> 00:01:27,679 Speaker 1: also why the devices have metal walls for reflection. You'll 22 00:01:27,680 --> 00:01:32,080 Speaker 1: often hear people say microwave ovens cook from the inside out, right, 23 00:01:32,680 --> 00:01:35,480 Speaker 1: that's the key to the speed. Think about it like this. 24 00:01:35,920 --> 00:01:38,400 Speaker 1: Let's say you're baking a cake in a conventional oven. 25 00:01:38,680 --> 00:01:41,160 Speaker 1: Normally you would bake it at three and fifty degrees 26 00:01:41,160 --> 00:01:44,640 Speaker 1: fahrenheit or a hundred and seventy seven degrees celsius. But 27 00:01:45,240 --> 00:01:48,600 Speaker 1: this time you accidentally set the oven at six hundred 28 00:01:48,600 --> 00:01:52,920 Speaker 1: degrees fahrenheit. The outside of the cake will burn before 29 00:01:53,040 --> 00:01:57,200 Speaker 1: the inside even gets warm, and you'll have ruined somebody's birthday. 30 00:01:57,680 --> 00:02:00,640 Speaker 1: In a conventional oven, the heat has to grate by 31 00:02:00,680 --> 00:02:04,880 Speaker 1: conduction from the outside of the food toward the middle. Hot, 32 00:02:04,960 --> 00:02:08,760 Speaker 1: dry air on the outside evaporates moisture, so the outside 33 00:02:08,800 --> 00:02:11,880 Speaker 1: can be crispy and brown like the crust unbread while 34 00:02:11,919 --> 00:02:16,160 Speaker 1: the inside is moist In microwave cooking, the radio waves 35 00:02:16,200 --> 00:02:20,200 Speaker 1: penetrate the food and excite water and fat molecules more 36 00:02:20,320 --> 00:02:24,480 Speaker 1: or less evenly throughout. No heat has to migrate toward 37 00:02:24,600 --> 00:02:28,640 Speaker 1: the interior by conduction. There's heat everywhere all at once 38 00:02:28,720 --> 00:02:32,720 Speaker 1: because the molecules are all excited together. There are limits 39 00:02:32,760 --> 00:02:37,600 Speaker 1: to this, though. Microwaves penetrate unevenly in thick pieces of food. 40 00:02:37,680 --> 00:02:39,760 Speaker 1: They don't make it all the way to the middle, 41 00:02:39,919 --> 00:02:42,840 Speaker 1: and there are also hot spots that are caused by 42 00:02:42,880 --> 00:02:47,280 Speaker 1: wave interference. But you get the idea. The heating process 43 00:02:47,440 --> 00:02:51,800 Speaker 1: is different because you are exciting atoms rather than conducting heat. 44 00:02:52,280 --> 00:02:55,400 Speaker 1: Inside a microwave oven, the air is at room temperature, 45 00:02:55,720 --> 00:02:58,359 Speaker 1: so there's no way to form a crust. That's why 46 00:02:58,440 --> 00:03:02,720 Speaker 1: microwaveable pastries or hot pockets sometimes come with a little 47 00:03:02,760 --> 00:03:06,760 Speaker 1: sleeve made out of foil and cardboard. The sleeve reacts 48 00:03:06,800 --> 00:03:11,280 Speaker 1: to microwave energy by becoming very hot. This exterior heat 49 00:03:11,440 --> 00:03:14,680 Speaker 1: lets the crust become crispy, as it would in a 50 00:03:14,720 --> 00:03:22,080 Speaker 1: conventional oven. Check out the brainstuff channel on YouTube, and 51 00:03:22,120 --> 00:03:24,560 Speaker 1: for more on this and thousands of other topics, visit 52 00:03:24,560 --> 00:03:39,720 Speaker 1: how stuff works dot com.