FAA Ground School Practice Test

What is meant by the term "dewpoint"?

1. The point at which air pressure is equal to sea level

2. The temperature to which air must be cooled to become saturated

3. The temperature at which water freezes

4. The relative humidity at which condensation occurs

The correct answer is: The temperature to which air must be cooled to become saturated

The term "dewpoint" specifically refers to the temperature at which air must be cooled, at constant pressure, to achieve saturation—meaning that the air can no longer hold all of its moisture in vapor form, leading to condensation. At this temperature, the relative humidity reaches 100%, and any further cooling of the air will result in moisture condensing into water droplets, like dew. This concept is essential in meteorology and aviation because it helps predict weather conditions, visibility, and the likelihood of fog formation. Understanding the dewpoint enables pilots and meteorologists to assess atmospheric moisture levels, which can impact flight safety and weather forecasting. The other definitions do not capture the essence of dewpoint: the first option relates to air pressure rather than temperature and saturation, the third relates to the freezing point of water, and the fourth refers to relative humidity conditions rather than a specific temperature value.