Subject:  Re sodium street lamps (fwd)
Date:     Mon, 13 Apr 1998 123911 -0500 (CDT)
From:     "Roy L. Beavers" <rbeavers@llion.org>
To:       emfguru@hotmail.com
--------------------------------------------------


---------- Forwarded message ----------
Date: Mon, 13 Apr 1998 13:15:53 +1000
From: Stewart Fist 
Reply-To: fist@ozemail.com.au
To: "Roy L. Beavers" 
Subject: Re: sodium street lamps (fwd)

Sodium street lamps are quite unusual in the way that all their energy is
emitted in only two narrow bands of spectrum quite close together in the
yellow band.

Other forms of light are generally broad spectrum, either at the point of
emission, or through secondary radiation from the tube coating.

The eye relies on slight focus differences from broadband spectrums to handle
the fine focus mechanism, and so with sodium vapour lamps people with focus
difficulties (usually long-sighted) have trouble holding and maintaining focus
- and they eyes hunt for visual clarity.  This can produce headaches in many
people.


-- 
Stewart Fist - writer and columnist
See http://www.theaustralian.com.au/techno/columns/fist.htm 
       http://www.abc.net.au/http/sfist/         (some archives)
       http://www.electric-words.com              (main archives)
70 Middle Harbour Road, Lindfield, 2070,   N.S.W,   Australia
Phone +61 2 9416 7458                        Fax  +61 2 9416 4582



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Reprinted with permission of Roy Beavers, http://www.feb.se/EMF-L/EMF-L.html