Re: Water burns!

Mike Kaliski wrote:


That would be why returns on 3 Cm marine radar are wiped out in heavy rain
then. I can vouch for the fact that heavy rain and spray can result in 100%
obscuration of ship radar targets.

Aircraft also use radar to detect storms. The severity of the weather ahead
is determined by analysis of the probable size of the water droplets in the
cloud, which affects the level of the radar return.

While water molecules may have an inherent resonance at 1 THz, it is
generally accepted by the scientific community that microwave ovens work by
exciting water molecules, amongst others, in food. I can't recall ever
cooking anything in a microwave that wasn't wet or at least damp. Well I
have tested some bits of plastic for suitability for use at RF, but that
wasn't for eating - and the wife was out!!!

I am happy to accept that there is no direct correlation between the
resonant frequency of a water molecule at 1 THz and a microwave oven
magnetron operating in the Ghz range. However, microwave ovens will heat
even distilled water quite effectively and heating is defined as an increase
in vibrational energy of molecules. So however the process actually works,
some principle of resonance must exist to allow the excitation of the water
molecules to occur. Either that, or microwave ovens actually work by heating
the food with infra red radiation derived using waste heat from the
magnetron and we have all been fooled. :-)



Increased molecular motion certainly accompanies increased temperature, but depending on the water's salt content, the skin depth of water at microwave oven frequencies is 0.5cm to 4.7cm. So I guess it is an absorption phenomenon, rather than resonance. Or, infrared radiation from the maagnetron! ;-)

This information, BTW, comes from Ron Schmitt's "Electromagnetics Explained".

Chuck

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