In reply to veteye:
Phase has also nothing to do with it; the only significant thing is the frequency of the radiation (or wavelength, if prefer to think about things that way, the two values being directly related by the equation (frequency)x(wavelength)=(speed of light).)
The 'Cat 4' rating indicates a particular range of transmittance for light in the visible spectrum only.
Beyond that, *any* proper pair of sunglasses *should* filter 100% of UV (and IR) light - but again, that's not what the 'Cat' rating refers to.
Polarized lenses are helpful in reducing 'glare' (since light which is reflected off water becomes strongly polarized in one direction, so can therefore be selectively filtered out) but otherwise aren't relevant in this discussion.