Question

on what basis and how will you determine whether air is saturated with vapour or not

Answer 1

When the air contains as much water vapour as it can hold at a given temperature it is said to be saturated.

In order to find whether it's saturated or not we have to see the given below explanation :
With a fall in temperature, the capacity of the air to hold water vapour. Thus,air may becomes saturated when cooled. air make it saturated even without cooling if evaporation keeps on increasing the amount of water vapour in it.
When a temperature of saturated Air falls the air no longer able to hold the all the water vapour it is carrying the excess water vapour them changes into tiny droplets of water.
Hence, by condensing we can conclude that whether Air is saturated or not.

Answer 2

Whether air is saturated with water vapour or not in determine on the basis of the extent of water vapour present in the air if the relative humidity is hundred percent air is saturated with the water vapour in that case we can see the formation of water droplet on leave of plant or grass