Generally speaking, where in the microwave oven is it typically hottest? Typically there’s something like a 2 cubic foot, 3d space. Will stuff cook universally the same no matter where it is placed? Or do some spots in the oven get hotter than others?
The microwaves are created and then sent into the main chamber, where they bounce back and forth from wall to wall until they hit some food and get absorbed (heating up the food). So more or less the same amount of heat should get into the food no matter where it is. Some parts might get hotter than others, but that really depends on the exact shape and composition of the food, so you can’t say there’s a spot that’s always hotter.
Don’t you end up with standing waves in the chamber, though? The hottest spots would be the antinodes, with the nodes being cool. That’s why most ovens nowadays have a turntable, so no one bit of food gets stuck in a node.
I suspect it would vary from unit to unit.
Based on the microwave I bought last year, I’d say near the center. I’ve reheat two pizza slices where the one near the center was piping bubbling hot while the slice off to the side was remained refrigerator cold.
It’s ancedotal, but mine is always away from the center. Whatever is on the edge of the plate gets hotter. My daughter loves chicken nuggets, and after a minute or so, the nuggets in the middle of the plate are still cold while the outer nuggets are much hotter, so I switch them around and finish cooking. My microwave also has a turntable, if that matters.
Higher quality microwaves have either rotating turntables to move the food around, or fan-like things (‘impellers’?) that rotate to bounce the microwaves around the chamber in different directions. So the heating ought to be pretty even all throughout the chamber – in good quality microwave ovens.
If you are interested in testing out your own microwave, I recall a Consumers Reports test from the early days of microwaves: cover the bottom of your microwave with slices of bread, then on each one place a pre-cut slice of cheese. After running the microwave for a short time, you should be able to easily see if there are ‘cold’ spots where the cheese isn’t melted, and if there are any ‘hot’ spots where the cheese is overheated.
A “stirrer” is the term of art for the fan-like thing which helps to break up standing waves.
Another easy test is to fill the the oven chamber with small cups or bowls of water. Some will boil long before the others.
A layer of chocolate chips or miniature marshmallows will melt and show not just the hot spots but the actual wave forms. Measure the wavelength, check the sticker on the back of the oven for the frequency, and you can calculate the speed of your microwaves.
If you do this, note that the distance from one hot spot to the next, or from one cold spot to the next, is half a wavelength.
Most microwave ovens use a frequency somewhere close to 2.45 GHz. That works out to a wavelength of about 12.24 cm.
Half of that would be 6.12 cm or a little less than two and a half inches.