Grades K–2 · Earth & Space
What is fog made of?
A familiar tree can look pale behind fog because tiny water drops hang in the air near the ground. This low cloud holds liquid drops much smaller than raindrops, which can drift with the air.
Before those drops formed, some of the water was invisible water vapor, a gas mixed with the air. When moist air cools enough, some vapor can change into liquid drops. Many drops together make the pale cloud we can see. Different weather conditions can bring about that change.
The Enlarged drops circle represents tiny liquid drops in the near-ground fog. The pale layer over the trees shows the changed view when those drops scatter light.
In the diagramFog is a cloud of tiny drops near the groundEnlarged dropsThe drops hang in air close to the ground.The trees are still there behind the fog.
The drops scatter light in many directions, changing both light from the distant tree and other light reaching your eyes. The tree can look pale or hidden without disappearing. Water that was invisible vapor has become drops that change the view through the air.
About this explanation
Starting knowledge: Recognizes air, liquid water, and familiar objects at different distances.
Sources
- National Weather Service — How Fog Forms
- National Weather Service — Social Media: Fog Safety
- National Weather Service — Radiation Fog