How do Polaroid sunglasses cut the glare off water and roads?
Light reflected off horizontal surfaces (water, wet roads, car bonnets) is mostly polarised horizontally.
Light reflected off horizontal surfaces (water, wet roads, car bonnets) is mostly polarised horizontally. Polaroid sunglasses have their transmission axis vertical, so they block that horizontally-polarised glare while still letting through the useful, randomly-polarised light of the scene. This only works because light is a transverse wave that can be polarised.
Key point
Reflected glare is horizontally polarised; a vertical polariser blocks it.
Common mistake
thinking the glasses just darken everything equally like a tint.
Memory tip
glare is polarised — a crossed axis wipes it out.
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