SUN GLASSES

At 11:02 13 June 2013, Doug Mueller wrote:
DO NOT FLY WITH NON POLORIZED LENS!
by doing so you trick your eye into opening wider
because of the
shade. Remember polorization is used to protect
from UV light. If
you open your eye wider by non polarized glass you
expose your
eye to that UV light. You will damage your eye much
quicker. It is
not a function of can you see your instruments or
not. Do not be
mislead into this kind of thinking......
Most glider canopies are not made with polorized
protection.


Er no, actually. Polarised sunglasses block a portion
of the incident light according to how it is polarised,
not by wavelength. Reflected light is partly polarised,
which is why polarised sunglasses reduce glare.

UV protection is accorded by the tinting medium.
There are plenty of substances out there that block
UV, just as there are tints that block other
wavelengths (hence coloured lenses).

There are a number of standards around for
manufacture of sunglasses based on opacity to UV
(no agreed international standard yet), including an
EN standard in Europe and an ANSI standard in the
US. These specify the maximum transmittance in the
UV part of the spectrum as a percentage of the
transmittance in the visible part.

Naturally your eyes will open wider if the amount of
visible light getting to them drops- the point is that a
very much less of the light getting through is UV.

I don't know about your part of the world, but in
Europe most good sunglasses are sold with a CE
mark indicating that 95% of radiation at 380Nm is
blocked.

None of this has anything to do with polarisation.

In short, check the specified UV transmittance.
Polarisation is just a personal preference.