ANS:C - Wet bulb

The wet bulb temperature is a measurement commonly used in meteorology and psychrometrics to describe the cooling effect of evaporation on a thermometer bulb that is moistened with water. Here's how it works:

1. Setup: A thermometer is wrapped with a moistened cloth or wick. As air flows over the wet cloth, it evaporates the water, causing the temperature of the thermometer bulb to decrease.
2. Evaporative Cooling: The evaporation of water from the wet cloth absorbs heat from the thermometer bulb, leading to a reduction in temperature. This process mimics the cooling effect experienced by human skin when sweat evaporates from its surface.
3. Measurement: The wet bulb temperature is the temperature indicated by the thermometer bulb when it reaches a state of equilibrium with the surrounding air through the process of evaporative cooling. It represents the lowest temperature that can be achieved by evaporative cooling under the prevailing conditions.

The wet bulb temperature is an important parameter in psychrometrics for calculating various properties of air, such as relative humidity, dew point, and enthalpy. It is typically measured using a device called a psychrometer, which consists of two thermometers—one with a dry bulb (unmoistened) and one with a wet bulb (moistened). By comparing the readings of the two thermometers, one can determine the wet bulb temperature and use it in conjunction with other atmospheric measurements to analyze air conditions.