The dew point is defined as

The dew point is defined as

• A. The temperature at which air becomes saturated at constant pressure
• B. The temperature at which water vapor condenses at all relative humidity
• C. The temperature at which air expands
• D. The temperature of maximum density of air

Answer: (A)

Dew point is the temperature to which air must be cooled, at the current pressure, for it to become saturated with water vapor. At that temperature, the air can no longer hold all the water vapor it contains, so condensation begins and dew can form. The higher the moisture content in the air, the higher the dew point; drier air has a lower dew point. For example, if air is at 25°C with a dew point of 12°C, cooling the air to 12°C would bring it to saturation and dew would form. This definition focuses on the exact point when saturation occurs, not on other unrelated ideas like the temperature at which air expands or the temperature of maximum density.

Dew point is the temperature to which air must be cooled, at the current pressure, for it to become saturated with water vapor. At that temperature, the air can no longer hold all the water vapor it contains, so condensation begins and dew can form. The higher the moisture content in the air, the higher the dew point; drier air has a lower dew point. For example, if air is at 25°C with a dew point of 12°C, cooling the air to 12°C would bring it to saturation and dew would form. This definition focuses on the exact point when saturation occurs, not on other unrelated ideas like the temperature at which air expands or the temperature of maximum density.