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• C$16 for C$150 toward a complete pair of prescription glasses or Prescription sunglasses

Polarized Lenses: Blocking the Glare

The inventory includes sunglasses with polarized lenses. Learn exactly what that means with Groupon’s introduction to this technology.

When light leaves the sun, it’s kind of aimless. As a ray barrels through space at the speed of, well, light, the advancing electromagnetic field that makes up a light wave fluctuates in strength around the direction of the ray in many different planes.

It’s the job of polarized lenses to get this erratic light in line. A polarizing filter consists of microscopic crystals in which strands of molecules are all aligned parallel to each other. When unpolarized light hits the filter, those molecule chains absorb any energy that’s traveling in the same plane they’re aligned in, blocking it from passing through. What emerges on the other side is now polarized, with all its energy fluctuating within a single plane.

Why worry about how a wave of light gets to you at all? As anyone who’s ever squinted through the too-bright reflection from a car’s hood or a body of water can sense, light polarized in certain directions can be dangerous. When light bounces off horizontal surfaces, it becomes horizontally polarized, resulting in the blinding phenomenon known as glare. For this reason, sunglasses with polarized lenses are coated with (or, in some cases, formulated containing) a filter that blocks this horizontal light, allowing through only the gentler vertical components in the environment. This improves safety for drivers, beachgoers, boaters, and whale ranchers, although not for downhill skiers—on the slopes, you need to see horizontally reflected light to alert you to icy patches ahead.