MICROWAVE OVENS
Q. Do microwave ovens kill bacteria in food?
A. No, not directly - even if you arranged the isolated bacterial cells somehow on a plate in the oven and switched it on. Microwaves don’t even kill fruit flies that can be seen flying around inside the MW oven while operating!
The reason is that the MW energy at the frequency of 2,450 MHz produces a wavelength of about 12 cm, good for heating a cup of coffee or a slab of meatloaf, but too small to have any effect on very small objects. Try putting a single drop of water on a glass plate and watching to see if it boils.
Fortunately, bacteria are invariably WITHIN the mass of food, such that the MW energy heats the water, oils, and fats to a depth of about 3 cm on all sides, and convection and conduction carries the heat to deeper regions. So it's the hot food food itself that kills the heat-labile (vulnerable) bacteria, not the exposure to microwave energy.
Q. Do microwave ovens make food radioactive?
A. No. This idea probably started with the early M/W ovens which were produced by Amana, and were sold under the name of "Radar-range", suggesting some form of penetrating radiation. The energy that is produced is on the electromagnetic spectrum in a range that is non-ionizing. In other words, microwaves cannot cause damage to the DNA, that could start the process of tumor production. Nor does M/W energy cause the food to be radioactive, or to demonstrate any form of residual effect. M/W energy causes food to HEAT UP. That's it. It does this by a process of flip-flopping the magnetic field so rapidly that the molecules of water and fats and oils in the food heat up.
Public health and safety agencies and personnel around the world have been watching for any injury caused by a microwave oven since they were first introduced to the retail market around 1968, and there have been none.
It could be argued that M/W ovens are actually more safe that conventional ovens and stoves.... When for instance did you hear of a M/W oven causing a stove-top fire, or producing dangerous gases or fumes, or causing a canopy grease-fire?