How does a psychrometer measure relative humidity

Question

It compares the temperature and the wet air and dry air
It compares wet air and dry air at two different elevations
It compares to level of moisture in the air at different times of the day
It compares the temperature to the level of moisture in the air

Answer 1

A psychrometer measures relative humidity by comparing the temperatures of a dry bulb and a wet bulb. The two thermometers (one measuring the temperature of the air and the other measuring the temperature of the wet bulb, which is cooled by evaporation) allow for the calculation of the relative humidity based on the difference in their readings.

Therefore, the correct answer is:

It compares the temperature and the wet air and dry air.