The control panel of a microwave oven. Microwaves are electromagnetic waves of length 0. 1 to 30 cm; those used in microwave cooking have a wavelength of 12cm. They cook rapidly by causing the water molecules contained in the food to vibrate at 2450 million times per second, thus heating it up. The microwave energy does not heat the utensils in the oven because the materials of which they are made do not absorb energy from the magnetic field. .