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Date:         Mon, 10 Aug 1998 06:58:41 -0400
Reply-To:     David Bogle / Architecture <bogle@BWAY.NET>
Sender:       Vanagon Mailing List <Vanagon@vanagon.com>
From:         David Bogle / Architecture <bogle@BWAY.NET>
Subject:      Re: Driving/Fog Lights
Comments: To: "Dr. Rainer Woitok" <woitok@RRZE.UNI-ERLANGEN.DE>
Comments: cc: Vanagon@VANAGON.COM
Content-Type: text/plain; charset=us-ascii

Hello,

I must share this with the group. In my high school physics class, which was taught by a naval engineer, die-hard VW oval-window beetle driver, (never waxed that grey paint, but it ran like a champ,) I learned that the light from burning sodium, a "yellow" light, was not only in the middle of the visible spectrum, but that its frequency or wavelength was the same dimension as the diameter of a typical water droplet in fog! This means that (we're talking about the wave theory of light here, not particle theory) the wave, enters the droplet and leaves the droplet at the same angle; and it reflects back at the same angle therefore cancelling out its own reflection. Of course, some of it is reflected back, but overall the depth into the fog which one can see with yellow light is greater.

This is how I remember it, now 20 years later.

David Bogle '72 2.0l BrooklynCampmobile soon to be owner of '88 Westfalia

Dr. Rainer Woitok wrote:

> Hi all, > > On Thu, 1998-08-06 17:59:25 -0700, David Marshall wrote: > > > ... > > If you want to see in the fog, then yellow yellow/blue light is what you > > want. > > That's not correct. It's true that fog tends to absorb less light in > the yellow range and more in the red and blue ranges. But there's > absolutely no need to emit yellow light in the first place. Yellow > tinted glasses will absorb ligt of any color, some colors more, some > less, but they will also absorb _yellow_ light. The light produced by > the bulb is more or less white, that is it's a mixture of light with any > wavelength (or any color). Thus use clear glasses to send as much light > as your bulb produces into the fog and let the fog filter out the red > and blue colors and mainly allow the yellow part of your emitted light > come back to you. > > What mainly makes foglights foglights is the special construction of the > lens and the fact that they are mounted relatively low above the ground. > > Sincerely > Rainer > > ---------------------------------------------------------------------- > | Rainer M Woitok | Phone: (+49-9131) 85-7811, -7031 | > | Regionales Rechenzentrum | | > | Friedrich-Alexander-Universitaet | Fax : (+49-9131) 30 29 41 | > | Martens-Strasse 1 | Telex: d 629 755 tf erl | > | D-91058 Erlangen | | > | Germany | Mail: Woitok@RRZE.Uni-Erlangen.DE | > ----------------------------------------------------------------------


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