Mirage
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Why Do Roads Look Wet on a Hot Day? The Science of Mirages
Have you ever been walking or driving on a hot sunny day and noticed that the road ahead looks shiny, as if it’s covered with water? Then, as you get closer, the “water” mysteriously disappears. That’s not your eyes playing tricks on you—it’s a natural optical phenomenon called a mirage, and the science behind it is fascinating.
What Causes a Mirage?
On very hot days, the ground gets heated by the sun. The air just above the ground becomes much warmer than the air a few meters higher up. Warm air is less dense than cooler air, and since light bends (refracts) when moving through air layers of different densities, this creates the perfect condition for an optical illusion.
When light from the blue sky travels downward, it bends as it moves through these layers of hot and cool air. At a certain angle, instead of escaping into the ground, the light undergoes total internal reflection—it bounces back upward toward your eyes.
Why Does It Look Like Water?
Your brain assumes that the light reaching your eyes has traveled in a straight line. So, when you see this reflected light from the sky, you interpret it as a patch of water on the ground (because water also reflects the sky). The result? A convincing illusion of a puddle or shimmering lake on the road.
posted by Lucian @ 1:32 PM
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