eric said:
Hi, I am having a little microwave experiment, and I want to shield some
cracks from leaking microwaves. A pal said to me that a paper-type
called "mica" is used for such reasons in microwave ovens. Actually what
he told me is that it allows microwaves to pass through, but it blurs
them so as they are not focused as before.
Is it true, or does anyone know any better way to make leaking
microwaves less harmful (apart from Faraday cage, this is too hard for
me to make, I suppose).
Mica is only used to cover the waveguide hole in the ovens because it does
not allow FOOD to pass through it. The microwaves pass through practically
as though it weren't there. Compared to plastic, mica has the advantage
that it doesn't melt or burn when it gets hot.
Metal foil will stop microwaves, but the microwaves can go around the edges
of the foil, unless the foil is continuously connected along the seams,
which is very hard to achieve. In some cases a wide overlap at the seams
will help but without knowing what you are trying to do, it would be hard
to give advice.
You need to get yourself a leakage detector, then you can tell whether you
have solved your problem or not. Get a meter that can show the amount of
leakage, not just one that has a light that indicates "too much" leakage.
If you get a meter that shows a reading that indicates the relative amount
of leakage then you can see if the meter is still working because you can
see the leakage of a normal oven. Any meter that only has a light
indicating "too much" leakage is inferior because a very high amount of
leakage could destroy the meter completely and you would then not know that
the meter was not working.
One of the best ways to reduce your exposure is distance. To a reasonable
approximation, the leakage power density will decrease with the square of
the distance. This means if you go ten times as far away from the oven,
the leakage will be 100 times less.
Chris
