Glares: How Do Sunglasses See Through Water?

Light waves from the sun vibrate in every direction—up, down, left, and right. However, when light bounces off a flat, shiny surface like a lake, a road, or a window, the waves all flatten out and vibrate in one direction (usually horizontally). This concentrated 'flat light' is the blinding white glare.

Polarized sunglasses are made with a special chemical film that acts like a picket fence with vertical slots. They only allow light waves vibrating up and down to pass through. Since the annoying glare is vibrating sideways, it hits the vertical 'slats' of the glasses and is blocked completely.

When the surface glare is blocked, your eyes can finally see the light that is reflecting off objects inside the water. This is why a fisherman wearing polarized glasses can see a fish swimming deep under the surface, while others only see a reflection of the sky.