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's a mineral, often associated with granite, it forms thin sheets.
Metal will reflect micowaves. If the leaks are small, patching with metal will work, if the enclosure is made to contain them as an oven is (that is a Faraday cage, btw). Whether you're using an existing system or a new one, take care with high power sources, as usually you need to make sure the energy is safely absorbed or dissipated somewhere.
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.
It is a classic experiment that proves that there is no ether. For various reasons we do not want to have microwaves leaking behind the surface they hit. I think the ideal for it would be some kind of material that "absorbs" the microwaves, as lead does for radiation. If you know such materials or have better ideas, it would be great to let me know.