Why can you see better into water with polarized glasses?

Many of us know we can discern more features in shallow lake water when wearing polarized sunglasses. It’s easier to see fish we want to catch, observe bottom features, or discover treasures like lost fishing lures with those glasses on. But how exactly do polarized lenses work?

They do it by filtering out reflected light. Light consists of waves that are oriented in all directions. Light waves that reflect off water (or any surface) are oriented horizontally – think of a flat sheet of paper, parallel to the water, coming toward you edgewise. That light is said to be polarized.

Now, the lenses of polarized sunglasses are specially treated so as to form filter that acts like a vertical picket fence (except that the spaces between the fence “slats” are extremely small). Imagine you’re holding a long rope that’s tied off against a tree. Between you and the tree is a picket fence, and the rope passes between two of the fence slats.

If you were to move your end of the rope rapidly up and down, you would create a wave in the rope, and that wave would pass right between the vertical fence slats and reach the tree. Now imagine moving the rope rapidly side-to-side. The narrow space between the slats would block the formation of a horizontal wave, which would never reach the tree.

That’s what polarized sunglass lenses do to reflected light. Light that would otherwise impede your ability to see into the water is filtered out before it hits your eyes. Light waves with a vertical orientation are allowed to pass through, revealing all those secrets from below the surface.

So, when on your lake exploring, wear your polarized glasses. You’ll get to know a little more about your lake. Not as much as if you looked below the surface through a snorkeling mask – but that’s a subject for another time.