Question

On an increase of absolute humidity and temperature, what is the effect on the relative humidity?
A) Increase
B) Decrease
C) Maybe increase
D) Maybe decrease

Answer 1

Hint: Relative humidity is used in weather forecasts and reports. It is expressed in percentage. The main difference between absolute and relative humidity is that relative humidity is independent of temperature whereas absolute humidity is not.

Complete step-by-step answer:
Humidity is the amount of water present in the air. Relative humidity is defined as the ratio of partial vapor pressure of water in the air represented by $p_{H_{2}O}$ to the saturation vapor partial pressure represented by ${p^{\ast }}_{H_{2}O}$, relative humidity is given by the formula $\varphi ={\displaystyle \frac{p_{H_{2}O}}{{p^{\ast }}_{H_{2}O}}}$ . Here $\varphi$ is relative humidity. We can understand saturation vapor partial pressure as the vapor pressure when the water content is at saturation level. At saturation level, an equilibrium has been established. This means an equal number of water molecules are evaporating from the surface of liquid water and an equal number of water vapor molecules are condensing back into the water.

Absolute humidity is defined as the total mass of water vapor in a given volume. It is not dependent on temperature. There is an inverse relationship of relative humidity with temperature. This means on increasing temperature, relative humidity decreases.

Thus the correct answer is option ‘B’.

Note: It is important to know that humidity can be expressed in three ways: Relative humidity, Absolute humidity, and Specific humidity. Absolute humidity is independent of temperature whereas relative humidity is dependent on temperature. Relative humidity is used in weather forecasts and is normally expressed in percentage.