This is a question that I was interested in on a practical level a number of years ago. It is now theoretical, but the answer still interests me.
Before I moved from the US to Israel, I participated in a mailing list for people making that move. We would talk about what appliances to buy, whether to buy them in the US or Israel, and if we brought our American appliances, could we use a transformer (Israel uses 220 current).
I had a microwave oven in the states that I wanted to bring to Israel and use it with a transformer. At one appliance store they told me that I had to buy a new microwave (one that ran on 220). Their reason was that not only does the current change between countries but the frequency does as well (from 60 to 50 Mhz, I think – the numbers could be off). They said that if the frequency was different, the holes on the screen of the microwave oven would be too big for the microwaves, and they would escape.
People on the list thought this was unlikely, but no one ever gave a proof one way or another. Anyone here have more serious information?
The shield must have holes smaller than the wavelength (which is about 12cm for microwaves). I don’t see what the frequency of the power source has to do with anything, except whether the device will actually operate at all.
I agree, that particular explanation sounds bogus. As far s I know, icrowave ovens generate a specific frequency, not some multiple of the supply frequency. I live in Japan where half the country uses 50Hz and the other half 60Hz, and I haven’t seen any warning labels or heard scary stories about microwaves. (We do need to watch out for washing machines and other appliances with big motors - they rotate faster with 60Hz. Timers built into appliances run faster too.)
But why would you want to take your microwave? They use a lot of energy, so you need a pretty big transformer - have you looked up their prices? They’re not cheap. I think it would be more economical to sell yours in the US and buy a new one in Israel.
As I mentioned, the question is now academic, not practical. I did buy a new microwave here, primarily because of the size (and expense) of a transformer necessary for a microwave.
The idea the storeowner said was that the size of the microwaves was determined by the frequency of the electricity.