Mirage
Beginner
Light bends in layers of air at different temperatures.
Hot air near the ground has lower n, so light bends upward gradually giving an inverted image of the sky that looks like water.
Seen on hot roads.
It's refraction, not reflection from a surface.
In more detail
A mirage is an optical illusion caused by refraction through layers of air with different temperatures. Hot road surfaces create inverted reflections that look like water.
Real-world uses
- Pilots and drivers can misjudge distances in mirages.
- Scientists use mirages to study atmospheric temperature gradients.
- A shimmering patch on a hot road looks like water, because light bends through layers of air with different temperatures.
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Frequently asked questions
Why does a road look wet?
Light from the sky bends through hot air near the surface and reflects, creating an image of the sky.
Are mirages in cold places?
Yes, inferior mirages occur above cold surfaces, and superior mirages occur over cold water.
What causes a mirage?
Hot air near the ground has a lower refractive index, so light from the sky bends upward toward the eye.
Related topics in Optics
Dispersion · Rainbow formation · Scattering of light · Refraction at a spherical surface · Thin lens · Lens formula