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Microwave Radiation
 Since 1971 the FDA has regulated the
amount of radiation that can leak out of a microwave oven. A microwave
oven can have no more than 5 mW of radiation per square centimeter 2
inches from the oven itself. Radiation is a general term that is
referring to the microwaves (electromagnetic waves). However,
microwaves are not very dangerous compared to other electromagnetic
waves, such as x-rays or gamma rays, that can damage cells in the human
body. Microwaves do not have enough energy to damage cells, but they
can cause burns in human skin and tissue.
 The
reason that microwaves do not escape from a microwave oven is that the
oven itself is a Faraday cage. A Faraday cage contains
electromagnetic waves, and does not let them escape. The oven's
walls are made of metal, which reflects microwaves. The door of
the oven also has a metal conducting shield on it. There are holes on
it so you can see the food inside, but the holes on it
are much smaller than the wavelength of the microwaves, so they cannot
escape. The same is true of the slits in a microwave oven for the
light and fan. They are small enough that microwaves cannot pass
through
them. Lastly microwave ovens have a safety feature that turns off
the magnetron when the door is opened, even if the time isn't up.
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