Q.Explain 'mirage' as an illustration of refraction.

[!TLDR] A mirage is caused by air's refractive index increasing with height above a hot road, bending distant light upward into the eye and making it seem to reflect off a nonexistent water pool. [!ANSWER] Hot air near the road has a lower refractive index than the cooler air above; a distant ray bends progressively toward t …

A mirage occurs on a hot, clear, sunny day along a level road, where a shimmering 'pool of water' appears to lie some distance ahead but recedes and vanishes on approach. The physical cause is refraction, not reflection: air directly in contact with the hot road is the hottest, least dense layer, and air temperature (and hence its refractive index) changes gradually with height -- refractive index INCREASES with height above the road, since cooler air is optically denser. A ray of light leaving the top of a distant object travels down through this vertical gradient of refractive index, bending progressively more toward the horizontal as it nears the road's hottest, lowest-index layer, and then curves back UPWARD once it can bend no further. To an observer, this upward-curving ray appears to originate from a point BELOW the road surface, precisely reproducing the geometry of reflection off an imaginary flat water surface at that spot -- e …

Explain the physical cause (a continuous vertical refractive-index gradient in hot air above a road) and trace how it bends a distant ray so it …

Describing a mirage as an actual reflection phenomenon, rather than correctly identifying it as pure refraction through a continuou …