It all depends on the microwave oven. The majority of ovens open with a mechanical lever (in many cases, can be also be opened by hand by grabbing the edge of the door) which will trigger a sensor that shuts down the emitter while the door is opening. Depending on how fast the door was opened, microwaves may still be bouncing around and could leak out.
OTH some ovens, like the more modern builtin cabinet microwaves, have an electronic button that shuts down the emitter before triggering the door latch/spring to open.
In any case, the duration and the amount of energy released during the opening motion vs. emission lag will probably not be enough to significantly harm you as dielectric processes need to establish a field to polarize molecules that will heat up as consequence.
Not enough to harm you, but how about a nearby device with an antenna?
Would a microwave burst e.g. fry the speaker of a crystal radio (where the antenna bridges nearly directly to said speaker) which happened to be tuned to a radio-band frequency for which 2.4GHz is a harmonic?
Or, for regulated products like 2.4GHz wi-fi routers, does FCC “accepts interference” testing take microwave bursts into account, or are we slowly degrading some component in them every time we open microwave ovens near them?
Anecdata, but for 2 years I have had a Chromecast Audio and a cheap Creative 2.1 system about 20cm away from my microwave, which is the type where you can just open the door to stop it. No problems so far.
Don't microwave ovens in large part depend on standing waves (resonant with the chamber size) to deliver the power levels they do?
Directed microwave energy can ruin electrical equipment nearby. You can find videos of this on YouTube, usually out of Russia.
Whether it'd do the same with a very short, unfocused momentary burst from reflection inside the oven cavity depends on your equipment I guess. I wouldn't leave my hackrf with RX amp turned on nearby, anyway.
If opening the door shuts down the emitter, then there'll necessarily be a brief period of microwave emission. Even if the emitter's power goes to zero instantly (it doesn't) then the microwaves that have been emitted and are still bouncing around can escape, that'll be quite a few nanoseconds.
I suspect the mechanical-style door switches on microwave ovens require some amount of door movement/opening before activating. The door is also I believe a part of the RF shield that contains the microwave radiation. As it opens and allows a gap before the off-switch activates — this seems likely your window of microwave leakage — not so much the residual waves that might linger after the device is powered off.
Pretty much. The cavity magnetron is highly resonant, I doubt it shuts off in less than 50ms or so. Same with transformer feeding it. Takes a bit for the magnetic fields to die out.
I wouldn't worry about it personally. The biggest danger is cooking your eyeballs and a few milliseconds isn't enough
at a previous job I was sitting in the break room with a then-coworker.
A very funny older coworker of ours entered and went to heat something in the microwave. After waiting a couple of minutes he decided he'd crack the microwave open and check on his food.
The machine was old and malfunctioning and somehow the latching mechanism failed and the microwave didn't stop running! The older fellow, being fairly quirky, didn't think twice and stuck his head right in the running microwave to spy on his food.
We yelled in chorus "NO $NAME NO! Get out! Close the door!"
One of the strangest, and funniest things I'd seen at that place (and there had been ...many).
What do you figure a few seconds of a human head in a running microwave would do?
Hahahaha that's awesome. he's prolly okay, skull is sorta thick and humans have lots of water.
I have heard that pain will warn you before heat damage is done, at least for realistic power levels and frequencies. And not including the eyes because they have poor blood flow and little feeling beneath the surface. Not sure where I heard that though, so it could be BS.
Nothing happens instantly. I'd assume after opening the door cuts the power you still have 1/120 of a second or more where the magnetic field in the transformer is collapsing and it's still generating microwaves.
