From: SFPhysics@aol.com
Date: Mon Feb 05 2001 - 03:17:23 PST
From: SFPhysics@aol.com Message-ID: <21.704b61f.27afe5c3@aol.com> Date: Mon, 5 Feb 2001 06:17:23 EST Subject: UV transmission by "glass"
> Can you tan through glass?
> If that were so, then I guess in high latitudes people who like to tan
> would have glass rooms to lay in, instead of the tanning saloons.
> Are there different types of glass and could you purchase a tanning glass
if you
> wanted to? What rays go through glass? Surely the infrared, since we can
warm
> up behind glass. Are the infrared in any way responsible for the tan?
> Thank you in advance,
> Alejandra
>>
Hello Alejandra:
Average glass will pass a wide range of the electromagnetic spectrum. There
isn't much of the spectrum that will not pass through glass. Radio waves,
microwaves, IR, visible light, UVA & lower UVB, X-ray, Gamma, Cosmic Rays,
all find glass generally transparent. Only a few portions of the EM
wavelengths are attenuated by common glass. Standard "soda" glass will do
little to stop ultraviolet radiation UVA and parts of UVB, the radiation
responsible for tanning and skin cancer. Ultraviolet radiation makes you tan
by damaging skin cells which react by making melanin, a dark pigment that
somewhat shields out UV radiation. I have not differentiated in detail here
about the UV wavelengths as the spectrum is more wide than the visible
spectrum by far and would complicate the discussion. However, glass can be
"doped" with metal oxides, rare earths, elemental gold, etc., to be opaque to
various parts of the electromagnetic spectrum. Modern automobile glass is
just such a mixture. It is designed to shield out much of the UVA, UVB, and
UVC radiation responsible for damaging the long chain hydrocarbons of the
plastic car interior. In doing so it reduces the damage to skin cells of the
people riding in the car.
You can tan through glass. The rooms of glass were called Solariums where
the sun's heat (IR) came through to make you feel good even though snow
outside may have been 2 meters deep. Most hospitals still have solariums.
A tan is a reaction to skin damage by UV not IR. Sunburn for any race of
people regardless of how dark the melanin pigmentation is should be of some
concern since what follows the permanent skin damage is skin cancer.
Therefore, it is not a good idea for anyone to get a tan by either the sun or
a tanning salon as all damage is additive leading to later serious skin
problems. The tanning salon may even do more damage as the mercury
vapor/argon spectrum used to "tan" is in some of the most dangerous
wavelengths. Even normal fluorescent lamps have a certain amount of unwanted
UV transmission that causes furnishing to fade and can damage sensitive skin.
More can be found at:
< http://www-nehc.med.navy.mil/downloads/ih/11.pdf >
Hope that helps.
Al Sefl
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