I was told the biggest risk from microwave exposure was heating of the water in living tissue. Examples of organs with the most water are the eyeballs, and anecdotally, someone told me he felt the pressure in his eyes from being at head level to a microwave with a malfunctioning door interlock.
So don’t look at a microwave in that case. If an appliance is malfunctioning, and you don’t want to get your hands and face next to the OFF stitch, you should pull the plug instead.
Important safety tip. Don’t microwave explosives.
If you aren’t microwaving some sort of explosive chemicals, I can’t see this even happening at all. A microwave is just a magnetron (a little thing that spins around and makes radio waves), a waveguide (aka a metal tube) and a metal box. That’s it. Maybe add in a rotating plate at the bottom and of course you’ll need some sort of control circuitry, which can be as simple as a mechanical timer or it can be a fancy microcontroller based thing. The most that it can do is heat your soup, and superheated soup that explodes just makes a mess inside the box. It doesn’t blow out the door.
Any explosion that you can make that would be powerful enough to blow the door open will probably also damage the magnetron and the control circuitry. You aren’t going to end up with a working microwave. Even if you somehow did, though, there are safety devices built into the door that prevent the microwave from running if the door is opened (or blasted open).
So, what happens if an evil leprechaun sneaks in, rewires the microwave to defeat all of the safety devices, then blasts the box apart in a way that leaves the magnetron running?
First of all, keep in mind that even though people commonly refer to microwaving your food as “nuking” it, there’s no nuclear type radiation involved here. Nuclear radiation, as people generally use the term, is ionizing radiation like gamma rays. Microwaves use radio waves. Technically, radio waves are a form of electromagnetic radiation, but then, so is visible light, and when folks talk about radiation they typically aren’t talking about the stuff that comes out of the end of a flashlight. Microwave ovens use 2.54 GHz radio waves, which puts them in the microwave radio band. Makes it kinda obvious why they call it a microwave oven now, doesn’t it?
Cell phones, cordless phones, traffic signal detectors (well, older ones), automatic door openers like the entrance to your typical grocery store, wi-fi, and many other things use microwave radio waves. Radio waves are basically harmless, although they can burn you if you get bombarded by enough of them. The same thing happens with visible light, though. You wouldn’t want to stand in front of a Hollywood style spotlight, and plenty of evil young kids have fried ants to a crisp by focusing sunlight on them through a magnifying glass. As long as you are exposed to levels that won’t cook you, there’s no harm from radio waves. If microwaves were really dangerous at low exposure levels, we’d all be dropping like flies, because we are surrounded by the things.
The same is not true of ionizing radiation. Ionizing radiation, even at low power levels, is high enough in frequency that it can strip the electrons off of atoms and create ions (that’s why it is called ionizing radiation). Part way through the ultraviolet part of the spectrum is where electromagnetic radiation becomes ionizing, so all the stuff lower than that (visible light, infra-red, microwaves, short waves, long waves, etc) are all pretty much safe, and everything above that (UV, x-rays, gamma rays, cosmic rays) are all dangerous. Walking outside is actually more dangerous than using a cell phone. The radio waves from the cell phone aren’t ionizing. The UV light coming from the sun is. Want proof? It’s the UV rays from the sun that make the things you leave in your car fade, and UV rays are also a major cause of skin cancer. UV rays from the sun can also cause cataracts.
Since there is no ionizing radiation present around our seriously malfunctioning microwave oven, the only thing you need to worry about is getting cooked. Burns from radio waves can be very painful and nasty, as the radio waves tend to penetrate into your skin and cook you a bit from the inside out (that’s how microwaves cook your food, too). So unlike getting burned by picking up something hot, by the time you feel the heat and say ouch from a radio wave burn, the burn already extends much deeper into your body and has caused more damage.
So where exactly is the danger spot? Well, that depends on how much our microwave oven went kablooey. If the waveguide is still attached to the magnetron, then all of the radio waves are coming out of the waveguide. If the waveguide got smashed in the explosion, then the radio waves might be coming directly out of the magnetron. Without an intact box to contain them, the radio waves are going to disperse out into the room, losing energy very quickly as they spread out in all directions. This is the famous inverse square law. 2 feet away from the source, you get 1/4th the energy that you had 1 foot away. 3 feet away, you get 1/9th. 4 feet away, it’s 1/16th (it’s 1/[n squared], hence it’s called the inverse square law). So the power level drops off very quickly. I’d be a little leery about getting any closer than maybe 8 to 10 feet or so away from it. You can probably get a bit closer, but I personally wouldn’t take the chance.
2.54 GHz microwaves tend to be absorbed pretty well by things like water, fats, and certain sugars, which is what makes microwave ovens so effective at heating our food. 2.54 Ghz microwave radio waves don’t tend to be absorbed so well by things like paper, glass, and wood. The radio waves will induce eddy currents into nearby metal. If the metal is fairly thin, it might get hot, and that might catch something on fire. Otherwise, there’s probably not much risk of a fire.
Wait for the timer to expire, or if the timer circuit is completely mangled, or the evil leprechaun rigged it so that the microwave oven will never shut off, use something like a long broom handle so that you don’t have to get too close to it, and knock the plug out of the wall. Or, if you have access to the breaker that controls that outlet, just turn the breaker off.
My microwave pauses when I open the door. I do this often to stir the contents, then put the food back in, shut the door and hit start. This causes it to continue the original countdown. I’m pretty sure it is designed to be used this way, and doesn’t damage me or the microwave. It’s 5 years old now, and still working A-OK.
Suggested claim:
That’s the way most of them work these days.
Male Bio teachers are notoriously snarky.
Don’t think you actually need explosives. I had a roommate try to cook an egg in the microwave once. That blew the door right open. The kitchen was covered in egg shell and partially cooked egg. Microwave still works fine though.
I don’t know that I would recommend replicating the experiment.
At least he wasn’t a physics teacher.
When I was a young, elementary school age kid it was even worse! Opening the door too soon would expose you to the “microwaves” used in cooking!
Yeah, this was the late 70’s/early 80’s, but you couldn’t be too careful!
Actually, I don’t think a magnetron has any moving parts spinning around, other than the electrons flying through. It uses a magnet to pull the electrons into a curved path, past a bunch of resonant cavities, which resonate and emit photons, which go into the wave guide and then into your soup.
Minor nitpick, but it’s actually 2.45 GHz. (Not that the difference really matters.)
Recently the was a news story about mysterious signals in radio telescopes attributed to a microwave oven. I found this bit interesting:
I’m sure this emission is perfectly harmless to humans, but it’s still interesting that the microwave behaved so differently to a premature door opening vs. the OFF switch (or timer running out).
Not mysterious at all.
When you turn the oven off, it’s off.
When you open the door when it’s running, it’s on- until the interlock shuts it off. If the interlock is sloppy, the door will get partially open before the magnetron shuts down.
I’m pretty sure it wouldn’t be safe to eat soup with photons in it. Prove me wrong.
Or ask the aforementioned high school biology teacher about that.
It’s safe but extremely distasteful – some of those photons might belong Captain Kirk when he is beaming up. Ever wonder why Bones does not like transporters? It’s because he is opposed to cannibalism.
The US has a product safety commission that one would HOPE would not allow such unsafe products on the market. Granted, they don’t always catch things until they are reported. But i figure they’ve had decades now to figure out if microwave ovens are, in fact, unsafe, and so far, the only people worried about it is your co-worker, and whoever spread that nonsense.
That said, you are right – unless you actually test it yourself, or find the actual documentation on that testing of that specific microwave model, you can’t be 100% sure. No one here can tell you for sure that your specific model of microwave may have slipped through all that testing with a dangerous defect. So if this worries you and causes you undo anguish, you have three choices:
I choose 3, simply because I’m not insane. Well, not in that way, anyway.
Having used a microwave to do a number of chemical reactions (in my opinion, it’s not the worth the trouble and I’m not convinced the difference in heating really makes a difference), I’ve microwaved flammable and possibly explosive substances. A research microwave, these days, involves heavy glass pressure vessels and secondary containment just in case something goes boom. I’ve never worried about the food in my home microwave catching on fire and exploding.
Now, there are stupid things you can do with a microwave that will make life unpleasant. Heat something with a high fat content in plastic, for instance. I had to throw away a microwave once because someone did that.
For what it’s worth, the initial microwave heated synthesis papers all used custom lab-built equipment based on a consumer-grade microwave. Generally they’d do things like disable interlocks. The publishing houses won’t accept any papers these days using such equipment as the research-grade microwaves are now readily available for purchase, relatively cheap, and much, much safer.
This is a very pretty image.
I know we had a thread, which I missed, on “how fast is darkness.” Gonna look into that.
Similarly, you must be careful when opening your computer, lest all the data escape.
Multiple threads, in fact.
What is the speed of dark?, 07/07/2007.
Does darkness have a speed?, 12/23/2015.