If you are inside in an air conditioned room, why is it that your sun glasses get fogged up when you go outsid

Question

If you are inside in an air conditioned room, why is it that your sun glasses get fogged up when you go outsid

Answer 1

Your glasses are cooler than the temperature outside so the water vapour in the warmer air condenses on the colder surface.

Answer 2

The warm air outside normally has a high relative humidity.  The cold surface of your glasses cause this moisture to precipitate as visible microscopic drops of water.