How do polarized sunglasses work?

Polarized sunglasses work by utilising the physics of light.

Light travels as waves through the air. These waves vibrate in all directions. When light hits a reflective surface, all the reflected light then vibrates parallel to the surface. For example, light reflecting off the surface of water, the road or the bonnet of your car will vibrate in a horizontal direction.

This is called polarization.

The majority of reflective surfaces that cause us glare are horizontal. So polarized sunnies have polarizing filters set in a vertical direction. Only light vibrating vertically can get through the filter, everything else is blocked out. 100% of the reflected light is blocked.

So light reflected off a horizontal surface is blocked out in the same way that you can't walk through a narrow door while holding a broomstick horizontally across your body. They don't block out all the light because all the vertical components of the light still get through, and that is how you can see through them.

When light is scattered off atmospheric effects like fog or rain, the reflections are at all sorts of angles. Your polarized sunglasses will block out any horizontal components of the scattered light. This reduces the glare by as much as 60%.

Improved Visibility

The reduction of the reflected light makes it easier to see into water, beyond the surface when fishing or boating.

It makes it easier to detect underwater hazards like rocks and sandbars. It keeps your eyes more relaxed when not having to squint as much. This also reduces headaches from glare.

It makes driving more comfortable on your eyes, by reducing the effort to see details. You can more easily see the road markings through rain on the road. You can see further in fog or smog.

Why Are They Better Than Normal Sunglasses?

Normal sunglasses reduce all light equally. Polarized ones selectively block out light reflected off horizontal surfaces. This reduces much more glare. It is also possible to get polarized bifocal sunglasses , so that you have all the benefits of polarized sunnies while still being able to read in them.

The best polarized sunglasses are from reputable designers that specialise in sunglasses for watersports or driving. Some examples include Maui Jim Sunglasses (which I stock in my Carlingford store ), Oakley and Polaroid.

You can also transform prescription glasses into sunglasses with magnetic clip on sunglasses.