Final answer:
Microwaves cause polar molecules, such as water in food, to absorb energy and heat up due to dielectric heating. The absorption corresponds to an increase in rotational energy and warming of the food. This process is efficient because the microwave frequencies match the natural frequencies of the absorbing molecules.
Step-by-step explanation:
The impact microwaves have on absorbing materials, specifically food, involves the interaction of microwave radiation with water molecules present in the food. Microwaves are electromagnetic radiation with frequencies that can be produced by electronic circuits, and they can also occur naturally. They are in the radio portion of the spectrum, similar to infrared (IR) radiation but with frequencies that do not extend as high.
When microwaves are used in cooking, they are particularly effective because water molecules and other polar molecules in food absorb the microwave radiation. This is due to the ability of these polar molecules to try to align with the alternating electric field created by the microwaves, a process known as dielectric heating. This leads to an increase in the rotational energy of water molecules and corresponds to an energy increase, typically about 10-5 eV per molecule. The energy absorbed causes the temperature of the food to increase, warming it up quickly.
Understanding the interaction between microwaves and materials has applications beyond cooking in a microwave oven. It's also relevant for understanding thermal radiation, as any object above absolute zero temperature emits and absorbs electromagnetic radiation, including microwaves. In turn, when microwaves are absorbed, this can result in thermal effects similar to those produced by any heat source.