Posted by Larry Hoover on May 7, 2006, at 16:36:52
In reply to tinted windows, posted by saturn on April 29, 2006, at 20:13:45
> I've posted questions on this before, but thought I'd bring it up again.
>
> Does car window-tinting block UVA and/or UVB light?
>
> In other words will it protect your skin and eyes?Automotive safety glass blocks essentially all UVB, and the shorter UVA (higher energy) bands (less than 10% transmission), up to about 390 nm wavelength. The bands of UVA with nearly complete transmittance are roughly analogous in energy to the bulbs that people call black lights, the psychedelic poster thing.
There is always the possibilitity that a higher energy photon in the UVB band just happens to fail to strike an atom in the glass its trying to pass through. Photon transmission goes to zero, but may not be zero, in the UVB band. Thicker glass transmits less than thin. As you slide up into the UVA, % transmittance increases, but quite gradually, at first.
You can still get a sunburn behind auto glass, but it would take a lot longer than you would have required in direct sunlight. A lot longer.
If you can see the tint on a piece of glass, then bands in the visible wavelengths are involved, and that may or may not correspond to ultraviolet bands being similarly influenced. The UV protective coating that is put on sunglasses happens to be transparent in the visible range, i.e. it is clear and colourless. But it is opaque at ultraviolet frequencies. They are distinct properties.
Lar
poster:Larry Hoover
thread:638229
URL: http://www.dr-bob.org/babble/health/20060330/msgs/641034.html