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Date:      Tue, 25 May 1999 08:23:14 +0100 (BST)
From:      Duncan Barclay <dmlb@ragnet.demon.co.uk>
To:        "Matthew D. Fuller" <fullermd@futuresouth.com>
Cc:        chat@FreeBSD.ORG, CONDOR <condor@inreach.com>, Eivind Eklund <eivind@FreeBSD.ORG>
Subject:   Re: secure deletion
Message-ID:  <XFMail.990525082314.dmlb@computer.my.domain>
In-Reply-To: <19990524233433.D10261@futuresouth.com>

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On 25-May-99 Matthew D. Fuller wrote:
> On Fri, May 21, 1999 at 02:13:09PM +0200, a little birdie told me
> that Eivind Eklund remarked
>> 
>> You want to run them through a microwave oven first.  This will break
>> the recording material (not the plastic) into approx 1 inch long
>> areas, using a neat pattern of lightning to do it (I'm not kidding).
>> 
>> No prize but passing your physics class if you can say why it goes to
>> approx an inch long pieces, and all the effects then stop.
> 
> Wavelength of the (appropriately named) microwaves?
> 
> Microwaves use radio waves at the fundamental frequency of water, no?

Microwaves operate in the 2.4GHz ISM band, just like 802.11 wireless LAN.

Water resonates at about 20GHz, but with a low enough Q that the 2.4GHz gets
the molecules moving. One major reason for not operating at 20GHz is that
meat/food is very reflective to 20GHz (I can lookup the complex permativity
for you if you need it) so that microwaves don't get into the food.

Duncan

---
________________________________________________________________________
Duncan Barclay          | God smiles upon the little children,
dmlb@ragnet.demon.co.uk | the alcoholics, and the permanently stoned.
________________________________________________________________________


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