CBSE Class 10 Answered
Fog begins to form when water vapour condenses into tiny liquid water droplets suspended in the air. When the sky is clear at night, land surfaces radiate heat to space and therefore cool. Sea and lake surfaces do not, however, cool by more than a small amount overnight (much less than 1°C). If the air in contact with a surface is cooled to its dew-point temperature, small water droplets form.