If P_V is partial pressure of water vapour in air and P_S is saturation pressure of water vapour at same temperature, then relative humidity is equal to

Concept:

Relative humidity (ϕ):

If is defined as the ratio of the mass of vapour when air is not saturator to the mass of vapour when air is saturated. It represents the water vapour absorbing capacity.

\(\phi = \frac{{{m_v}}}{{{m_{vs}}}}\)

Also,

\(\frac{{{m_v}}}{{{m_{s}}}} = \frac{{{P_v}}}{{{P_{s}}}}\)

Therefore, \(\phi = \frac{{{P_v}}}{{{P_{s}}}}\)

Where, Pv = Partial pressure of vapour when air is not saturated; Ps = Partial pressure of vapour, when air is saturated(Psat).