|
Microwave antennas
|
Microwaves is a misnomer. There's nothing "micro" about them, in the scientific sense, which says that micro means "one millionth". The wavelength range of this radiation is about 3.0 cm to 1.0 mm, with the energies between 10
-5 eV and 0.001 eV.
As with infrared radiation, many molecules vibrate and rotate when exposed to microwaves. When a photon of wavelength 12.2 cm is incident on a water molecule, the molecule will rotate, since it is polar (has a positively-charged end and a negative-charged end) and wants to align itself with the incoming magnetic field.
The water in the microwaves has enough energy that makes water in the rotational state, move up an energy level. Thus heat is created and water is evaporates and causes food to be hot.
Microwave
|
|
A cup of water boils quite nicely in a microwave oven. Bread, on the other hand, will dry out since the water evaporates easily. A paper napkin will hardly heat up at all.
Besides ovens, we use microwaves for many kinds of communication. Most television satellites and dishes operate in the microwave region, and any kind of radar device is emitting and receiving microwave signals. Short-wave radio operators are using microwaves to talk to each other around the world, because these waves can travel much further than weak radio waves.
