Question

What is the effect of dryness of air on evaporation?

Answer 1

Hint: Evaporation rates are higher at higher temperatures because as temperature increases, the amount of energy necessary for evaporation decreases. The lower the relative humidity, the drier the air, and the higher the evaporation rate.

Complete answer:
Dryness of air increases the rate of evaporation of water. The greater the humidity of the atmosphere which is surrounding the water molecule, the rate of evaporation is slow. Thus, the rate of evaporation depends on the surface area, temperature and humidity.
 If we are saying that air humidity is high, then the amount of water vapor is high in air. So, now water vapor intake capacity of air is decreased. But evaporation is the process by which extra water vapor is added to the atmosphere. So, naturally with more humidity the evaporation rate decreases.
Relative humidity is related to the partial pressure of water vapor in the air. At $100\% $ humidity, the partial pressure is equal to the vapor pressure, and no more water can enter the vapor phase. If the partial pressure is less than the vapor pressure, then evaporation will take place, as humidity is less than $100\% $.

Note:
The dew point is the temperature the air needs to be cooled to in order to achieve a relative humidity of $100\% $. At this point the air cannot hold more water in the gas form. Higher dew points yield higher condensation rates. Meanwhile, temperature controls evaporation rates, so relative humidity depends on dew point and temperature.