http://www.deja.com/getdoc.xp?AN=518822619&fmt=text
<37d10109.20843771_at_news2.tin.it>
Nel messaggio sopracitato affermavo impunemente di non credere all'ipotesi che
le molecole di acqua in fase liquida abbiano una sorta di risonanza, cio� un
picco di assorbimento, a 2450 MHz, che � la frequenza usata nei forni a
microonde.
Finalmente ho trovato una conferma autorevole:
http://landau1.phys.virginia.edu/Education/Teaching/HowThingsWork/microwave_ovens.html
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.
Louis A. Bloomfield, Professor of Physics, The University of Virginia
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Received on Mon Sep 13 1999 - 00:00:00 CEST