[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

Re: Tinted headlight bulbs

Ian.McFetridge@biomeasure.com wrote:

>      light?  Why are fog lights usually yellow, that is a fairly long
>      wavelength of the visible spectrum (only reddish is longer).
>      is the next best, since it is the shortest visible light.  That is why
>      I don't understand the whole yellow light thing?

The colour has nothing to do with either the wavelength or the
associated decrement of decay in mediums.

The_only_reason for them being yellow is to make them stand out and be
visible for the oncoming traffic in the milky (fog, blizzard)
conditions. That's why they are always located under the bumper (coz fog
never touches the ground but rather hangs in about 15 -20 cm above) and
that's why their lens has so many dispersing stripes.
The fogs are meant to disperse light wide, not far.
BTW, that's why the fogs work only in conjunction with the Lows, coz the
Highs in the fog or snow blizzard would be suicidal.

The driving lights, OTOH, are mounted on the bumper and are a lot more
focused. Their purpose is to cut in the darkness as far as possible to
make the road more visible for you.

Fellow ex-military officers on the list (Unka Bart, Gross, care to
comment?) know that personnel carriers, trucks and tanks have special
"spectacles" put on in the full blown stealth combat guise. Those
"spectacles" are essentially steel headlight covers with narrow (~1-2cm)
slits with blue light filters.
Blue light is used in this application simply because of its
indetectability by air surveillance.

Thanks for the report, Ian. You confirmed my gut feeling that those
bulbs were a hype.
Igor Kessel
'89 200TQ -- 18psi (TAP)
'98 A4TQ
Philadelphia, PA