Question

The most comfortable value for RH is _____.
A. $10\%$
B. $30\%$
C. $50\%$
D. $90\%$

Answer 1

The relative humidity (RH) is defined as the ratio of the actual amount of water vapour present in a volume of air at a given temperature to the maximum amount that the air could hold at that temperature, expressed as a percentage.

Complete step by step answer: Sweat cannot evaporate into the air while the air is at 100 percent relative humidity. As a consequence, when the relative humidity is high, we feel much cooler than the real temperature. If the relative humidity is low, we will feel much colder than the real temperature and our sweat evaporates quickly, cooling us off. Therefore, the most comfortable relative humidity value is $50\%$, so it would not be too dry or too wet in this situation.
Hence, option (C) is the correct option.
Additional information:
For a given temperature, the ratio of the partial pressure of water vapour to the equilibrium vapour pressure of water is the relative humidity (RH). The relative humidity is dependent on the temperature and the strain of the environment of interest. The same amount of water vapour results in higher relative humidity in cold air than in hot air.

Note: In this question you are asked to find the most comfortable value of relative humidity. In both the cases of high and low relative humidity, we do not feel well comfortable but on average ($50\%$) we feel comfortable because it won't be too dry or would not be too wet.