what happens when the temperature of air decreases to the dew point or below the dew point

When the temperature of the air lowers to the dew point or below the dew point the water vapor present in air will change the phase from gas to liquid by the process of condensation.

Which then results into the fog, dew on leaves and clouds.

Explanation:

Dew point temperature means the temperature at which water vapors present in air change their phase from gas to liquid.
This happens by the condensation which is the change of the physical state of matter from the gas phase into the liquid phase and is the opposite of vaporization.
So changing the temperature of the air, the water vapors will turn into dew and fog.

Chlidonias Chlidonias · Answer 2 · 2018-10-18T17:58:51+02:00

When the temperature of the air becomes almost equal to the dew point the air becomes saturated and the relative humidity during this condition becomes 100%. If the temperature of the air decrease below the dew point the relative humidity will be 100% or exceeds 100%. This condition, when the temperature of the air decreases below the dew point is called supersaturation but most of the time the temperature of the air will be lower than the dew point.