There's a kind of FAQ on this, by the author of *How Things Work: the
Physics of Everyday Life*, Louis A. Bloomfield at
<http://rabi.phys.virginia.edu/HTW//microwave_ovens.html>. He says:
While most microwave ovens operate at 2.45 GHz, that frequency is
not a resonant frequency for the water molecule. In fact, using a
frequency that water molecules responded to strongly (as in a
resonance) would be a serious mistake--the microwaves would all be
absorbed by water molecules at the surface of the food and the
center of the food would remain raw. Instead, the 2.45 GHz
frequency was chosen because it is absorbed weakly enough in
liquid water (not free water molecules) that the waves maintain
good strength even deep inside a typical piece of food. Higher
frequencies would penetrate less well and cook less evenly. Lower
frequencies would penetrate better, but would be absorbed so
weakly that they wouldn't cook well. The 2.45 GHz frequency is a
reasonable compromise between the two extremes.
So water does absorb 2.4GHz radiation, but it's not a resonant
frequency. 'course, I wonder how those LAN technologies work in
the vicinity of microwave ovens.
Randolph
