Private Pilot Private Exam

When do clouds, fog, or dew usually form?

1. When humidity increases

2. When water vapor condenses

3. When temperatures rise

4. During nighttime

The correct answer is: When water vapor condenses

Clouds, fog, or dew typically form when water vapor in the atmosphere condenses into tiny water droplets or ice crystals. This process occurs when the air cools to its dew point temperature, which is the temperature at which air becomes saturated with moisture. As humidity increases and air temperature decreases, excess water vapor transitions from a gaseous state to a liquid state, leading to the formation of clouds, fog, or dew. While an increase in humidity is often associated with the formation of these phenomena, it is specifically the action of condensation that is the key process that results in visible moisture, such as droplets in clouds or fog, and dew on surfaces. Thus, the correct identification of this process is why B is the appropriate answer.