scattering light decreases visibility & water droplets scatter light ->  water droplets scattering light decreases the visibility  clouds are made of water vapor / rain droplets & fog is a kind of stratus cloud on the ground ->  fog is made of rain droplets  fog is made of rain droplets & rain droplets are a kind of water droplets ->  fog is made of water droplets  water droplets scattering light decreases the visibility & fog is made of water droplets -> water droplets in the fog scattering light decreases the visibility