What is the separation between hot spots in a 2.45 GHz microwave oven?

Answer 1

That's a very interesting question ... one that I've seriously been meaning to measure

for myself for a very long time but of course never quite got around to it.

The wavelength at 2.45 GHz is roughly 3 x 108/2.45 x 109 meters = 121/4 centimeters

(very round numbers).

Based on nothing but the seat of my finely tuned pants, I expect the spacing

of the RF standing waves in the cooking cavity to be related to that number,

and the structure of the hot spots to repeat with a period of either that or else

half of it. So before I set anything up, I would predict the separation to be

something close to either 4.8 inches or 2.4 inches.

Of course, now that you've asked and I've offered a blue-sky answer based on

nothing, I once again intend to measure it soon. I'll describe the method I plan,

but this is NOT recommended by anybody, least of all this website, and you did

NOT get this suggestion from any internet entity. (say that 5 times fast)

-- I'll make a sheet of ice, maybe a couple of inches thick, in a large disposable

aluminum pan in the freezer. With careful advance planning, I'll grease the pan,

and remove it after the freezing, leaving only the ice.

-- I'll take a sturdy, empty cardboard box of some kind, a few inches thick, stiff

enough to hold the weight of the ice, and small enough to fit into the MW. This

will get my test ice up off the bottom, where the standing-wave pattern may be

different from what it is out in the middle of the cavity.

-- I won't have to disable the turntable ('carousel') because ours hasn't worked

in months. But anyone else considering doing this experiment, in a controlled,

laboratory environment, with several OSHA, Fire Dept., and medical observers

present, which I am NOT suggesting that anyone consider doing, would want to

disable the turntable before proceeding.

-- I'll run the RF for maybe 15 - 20 seconds at a time, until I begin to see little

puddles developing on the surface of the ice. They may not all appear at the

same time, so it may take a few more shots to discern the overall pattern.

-- If a pattern does emerge, the spacing can be easily measured, after carefully

sliding the ice sheet out of the oven and immediately wiping up any spillage

before my wife comes in.

That's what I plan to do, but I am NOT recommending it for you.