Can microwave emitters serve as a makeshift home defence weapon?
Although many of us have MW ovens, I can name like one Saw movie and one DIY channel that showed it's potential to melt things, and I watch\read a lot of gore and torture on the web. It won't be used in a military context due to how power consumption and short distance make it useless. But in a Home Alone situation it seems promising, especially as a trap because you won't stop anyone with that immidiately.
My qustions are:
How a breaf exposure is dangerous, and can it be used not to harm but to scare off?
How it'd be treated legally due to it's weirdness?
What are general downsides of that, like reflecting it back to the sender or dealing irreversible fatal damage etc?
I'm stupid at basic physics so I'm sure I miss something.
It can. But the inverse square law makes it not as useful as you might think. What you want is a maser.
Microwave radiation isn't ionizing. That's the bad stuff. Once you leave the path of the radiation there will be no lingering effects other than burns you suffered while in the path. Microwave ovens were initially built to REVIVE cryogenically frozen hamsters. FCC questions can depend a lot on what's in your proximity. Urban or suburban environment, be careful. If you're on the back 40 they probably won't care unless you've leased part of the property for a microwave transmitter tower.
I don't think most people will ever have access to a maser under any circumstances. If I am wrong, please let me know.
I wasn't able to find much in the way of maser lethality, but apparently a 15w maser broadcasters can send photos to earth from Mars.
Edit:
I found this scurrilous web page that indicates a $1,500 "Maser rife" can kill 71 cows on a single charge but for some reason people only get knocked unconscious by it.
Once you leave the path of the radiation there will be no lingering effects other than burns you suffered while in the path.
I was a bit more interested in if it can accidentially clog the bloodflow in veins or muscles in a limb causing more unpredictable danger, or fry the head (eyes, brain) of a victim for a permanent eyesight or cognitive damage. All from a brief exposure lasting seconds.
No bigger damage than literally cooking the flesh would cause. The radiation is of the size that it interacts with molecules the size of water. Jiggling them and transferring some energy as heat. The radiation itself is largely harmless. And if you are in an area with any telecommunications equipment chances are your are bathed in it at the moment. Any danger from it arises from intensity. Much like light or heat etc. You absolutely could cook internal tissues. And as such it's not a great idea to mess with it if you really don't know what you're doing. That and the Transformers for the cyclotrons are especially dangerous as well as there are some toxic Rare Earth elements in the cyclotron itself that you don't want to mess with. They are honestly all more dangerous than the radiation being emitted.
Since we don't know where you live, nobody can tell you the laws.
For actual home defense at less than lethal means, buy a taser or shotgun with beanbag rounds or mace. Anything homebuilt is unreliable and could get you in trouble with intent laws or weapon manufacturing laws.
Think about it. Your house is probably wired for a maximum of 100A (maybe more if newer). A microwave oven uses 10A, typically. The maximum power you could put into an array of household microwaves would be the equivalent of ten microwaves.
Now if you considered all of this being converted to, say, an electric heater -- you could probably heat a fairly large space with this much energy -- probably even your house in a Minnesota winter if it was at all insulated. If you were to be able to direct this heat towards someone, it'd be like standing right in front of the furnace while it was on and blowing all of its heat at you. It'd heat you up real good, but you could always just leave that spot.
But with 100A, you could power a lot of LED lights, and very bright ones too. Like airport runway level bright. You're probably better off building something like that which you could shine at an intruder. Just don't blind yourself during testing ;)
Ah, but your house power would have no trouble charging a colossal bank of capacitors to provide a brief instantaneous kill shot. Also, I think the design would be improved if you added a wave-guided magnetron so that the energy was more directed, but I don't know much about that - I am more of a laser person myself.
It would be pretty hard to hurt someone with microwaves from an MW oven. The reflections inside the oven are necessary to heat anything by any significant amount.