Why is dew seen on grass during a cool night?
Answer and explanation
Correct answer: Water vapour condenses on cool grass
The governing concept is condensation, the change of water vapour into liquid water when air or a surface cools sufficiently. During a clear, cool night, grass loses heat by radiation and its surface temperature may fall to the dew point. Air touching the grass is then cooled; if it becomes saturated, some water vapour changes into tiny liquid droplets on the blades. These droplets are called dew, so option D is correct. Grass does not manufacture water, air does not disappear, and smoke is unrelated to the process. Dew is different from rain because it forms directly on a surface rather than falling from clouds. The exact amount depends on moisture in the air, cooling, wind, and the surface temperature.
Frequently asked questions
What is the correct answer to this question?
Water vapour condenses on cool grass
Why is this the correct answer?
The governing concept is condensation, the change of water vapour into liquid water when air or a surface cools sufficiently. During a clear, cool night, grass loses heat by radiation and its surface temperature may fall to the dew point. Air touching the grass is then cooled; if it becomes saturated, some water vapour changes into tiny liquid droplets on the blades. These droplets are called dew, so option D is correct. Grass does not manufacture water, air does not disappear, and smoke is unrelated to the process. Dew is different from rain because it forms directly on a surface rather than falling from clouds. The exact amount depends on moisture in the air, cooling, wind, and the surface temperature.
Which subject and chapter does this question cover?
This is a Class 12 Geography question. Chapter: Water in the Atmosphere. Topic: Humidity, evaporation, and condensation.
