Explanation:

Explanation: 
1. Dew: When the moisture is deposited in the form of water droplets on cooler surfaces of solid  objects (rather than nuclei in air above the surface) such as stones, grass blades and plant leaves,  it is known as dew. The ideal conditions for its formation are clear sky, calm air, high relative  humidity, and cold and long nights. For the formation of dew, it is necessary that the dew point is  above the freezing point.
2. White Frost: Frost forms on cold surfaces when condensation takes place below freezing point  (0° C), i.e. the dew point is at or below the freezing point. The excess moisture is deposited in the  form of minute ice crystals instead of water droplets. The ideal conditions for the formation of white  frost are the same as those for the formation of dew, except that the air temperature must be at or  below the freezing point.
3. Fog: When the temperature of an air mass containing a large quantity of water vapour falls all of  a sudden, condensation takes place within itself on fine dust particles.So, the fog is a cloud with its  base at or very near to the ground. Because of the fog and mist, the visibility becomes poor to zero.In  urban and industrial centers smoke provides plenty of nuclei which help the formation of fog and  mist. Such a condition when fog is mixed with smoke, is described as smog (will be discussed in  detail in next post). [Related Question Asked in Mains 2015: Mumbai, Delhi and Kolkata are the  three mega cities of the country but the air pollution is much more serious problem in Delhi as  compared to the other two. Radiation fog results from radiation, cooling of the ground and adjacent  air. These fogs are not very thick. Usual in winters. Fogs formed by condensation of warm air when  it moves horizontally over a cold surface, are known as advectional fog. These fogs are thick and persistent. Occurs over warm and cold water mixing zones in oceans. Frontal or precipitation fog is  produced due to convergence of warm and cold air masses where warm air mass is pushed under  by the heaviercold air mass. Precipitation in the warm air mass condenses to produce fog at the boundary of the two air masses. These are called frontal or precipitation fog. In fog visibility is less  than one kilometre.