The glass turntable of your microwave oven lets microwaves pass through. Then they bounce off a metal floor, back through the glass turntable, and are absorbed by the food.
Microwaves pass through most glass, paper, and plastics without heating them so food absorbs the energy. Microwaves bounce off metal containers so food does not absorb the energy.
Microwaves may not reach the center of a roast. The heat spreads to the center from the outer, cooked areas just as in regular oven cooking. This is one of the reasons for letting some foods (for example, roasts
or baked potatoes) stand for a while after cooking, or for stirring some foods during the cooking time.
The microwaves disturb water molecules in the food. As the molecules bounce around bumping into each other, heat is made, like rubbing your hands together. This is the heat that does the cooking.
NOTE: Do not deep fry in the oven. Microwavable cookware is not suitable and it is difficult to maintain appropriate deep frying temperatures.
Glass turntable
Metal
