Recording of Weather — Geography STD 7 — Question

The instrument used for measuring relative humidity is called a hygrometer. The hygrometer consists of wet and dry bulb thermometer. The dry bulb thermometer is an ordinary thermometer while the wet-bulb thermometer is kept wet by a wick that dips into a container of distilled water. The wet-bulb thermometer shows a lower temperature than the actual temperature as evaporation from the moist wick has a cooling effect. A larger difference between readings of two thermometers means low relative humidity and small difference means high relative humidity.