Heat is a form of energy and hot molecules are energetic molecules. So, the more energy they have, the hotter the temperature. In conventional ovens, Brill says heat is transferred from the air to food by collisions of hot, energetic air molecules with colder, less energetic food molecules. This happens at the surface of the food. The inside of the food is then heated by conduction as the hotter, more energetic molecules near the surface collide with the colderless energetic molecules inside.
Microwave ovens use an entirely different approach to heating food.
Microwaves are a type of radio wave, just like the waves from a radio station travel through the air and shake electrons in an antenna, microwaves shake water molecules in food. Because the waves can penetrate the food, the molecules in the center of the food are heated at the same time as those on the surface. This is the University Report, I'm Tracy Orillo Donovan.