Various types of fog are essentially clouds that form at the earth’s surface, produced by temperature differences and moisture in the air. As warm, moisture-laden air cools, its relative humidity (the amount of moisture that air can contain, which depends on the temperature) increases.
Warm air can hold more water vapor than cold air. So if the air is cooled sufficiently it will reach saturation, or the dew point, at which point the moisture begins to condense out of the air and form water droplets, creating fog.
- What is the author’s main purpose in this passage?
A. To describe various types of fog
B. To explain how fog is formed
C. To define relative humidity
D. To compare the effects of warm air and cold air
- This passage would most likely be written by …… .
A. an archeologist
B. a biologist
C. a meteorologist
D. a psychologist
- The word in bold “sufficiently” as used in the passage is closest in meaning to …… .
- The tone of this passage could best described as …… .
- It can be concluded from the passage that …… .
A. foggy days are caused by cold nights
B. fog is likely to form in desert areas
C. hot humid days are usually followed by cold, foggy nights
D. fog could form on a cold evening after a warm day