| A microwave oven works by passing microwave | | | | to heat from other methods. The rays from a |
| radiation, usually at a frequency of 2450 MHz | | | | microwave electrically manipulate water |
| , through the food. Water, fat, and sugar | | | | particles to cook food. It is actually the |
| molecules in the food absorb energy from the | | | | friction caused by the movement that creates |
| microwave beam in a process called dielectric | | | | heat and warms the food. The misconception |
| heating. Many molecules (such as those of | | | | arises because microwaves penetrate dry |
| water) are electric dipoles, meaning that | | | | nonconductive substances at the surfaces of |
| they have a positive charge at one end and a | | | | many common foods, and thus often deposit |
| negative charge at the other, and therefore | | | | initial heat more deeply than other methods. |
| rotate as they try to align themselves with | | | | Depending on water content the depth of |
| the alternating electric field induced by the | | | | initial heat deposition may be several |
| microwave beam. This molecular movement | | | | centimeters or more with microwave ovens, in |
| creates heat as the rotating molecules hit | | | | contrast to grilling ("broiling" in American |
| other molecules and put them into motion. | | | | English), which relies on infrared radiation, |
| Microwave heating is most efficient on liquid | | | | or the thermal convection of a convection |
| water, and much less so on fats and sugars | | | | oven, which deposit heat shallowly at the |
| (which have less molecular dipole moment), | | | | food surface. Depth of penetration of |
| and frozen water (where the molecules are not | | | | microwaves is dependent on food composition |
| free to rotate). Microwave heating is | | | | and the frequency, with lower microwave |
| sometimes incorrectly explained as a | | | | frequencies being more penetrating. |
| rotational resonance of water molecules: such | | | | |
| resonance only occurs at much higher | | | | Most of people do not think about microwave |
| frequencies, in the tens of gigahertz. | | | | spare parts when their domestic appliance |
| | | | breaks down. They would usually get it fixed |
| A common misconception is that microwave | | | | by a specialist who will buy the microwave |
| ovens cook food from the "inside out". In | | | | spare parts and do the work for you, or even |
| reality, microwaves are absorbed in the outer | | | | will buy a new one. One option they tend to |
| layers of food in a manner somewhat similar | | | | forget is they could fix it by themselves. |