Because the microwave energy is beamed into the interior of the microwave and then dispersed by a metallic "stirrer," the pattern of the energy can be fairly consistent, rather than completely random. But this pattern sometimes causes certain portions of the food to overcook (creating tough spots) and others to undercook. A microwave oven with a carousel is far better at cooking the food consistently--the pattern becomes quite random while the carousel is turning.
The glass tray has two proposes. It catches spills. It also raises the food off the floor of the microwave so that the microwave energy can reach the bottom of the food, too.
You can do a fair job with the inexpensive sort of tester that you can buy from a hardware store. To get a more accurate reading, contact a qualified appliance repair technician.
Not usually. As long as the microwave oven door remains closed and you make no direct contact with the inside of the oven while the oven is on, the energy is safe. If you were to operate the microwave oven with the door open, it would be dangerous.
Microwave energy penetrates foods much more deeply than conventional heating does. The water molecules inside the food heat as quickly as those on the outside. And water expands when you heat it. Eggs, potatoes, and other things with shells or skins explode because the expanding water has nowhere to go.
Some studies indicate a possibility for health problems with prolonged exposure to microwave energy. But most research has shown that it's very natural to be exposed to low-level microwaves--we get that exposure even from the atmosphere--without any adverse or lasting effects. Microwave ovens are required to meet very stringent federal government guidelines for leakage.
