Why do roads look glossy or wet on a hot day but disappear when you get closer to it?
In: Chemistry
The heat from the road creates a layer of hot, less-dense air above it. Light travelling from the cooler air above through the warmer air refracts, bending light from the horizon or sky towards you, thus why it has a lighter color.
The glossy effect is because the hot air is less dense and rising, being replaced by cooler air which is then heated by the road, creating a moving cycle which alters the exact amount of refraction occurring and thus making it look all shimmery.
The refraction only bends light so much though and thus usually requires a low viewing angle for light from the sky to be seen. As you get closer, the viewing angle increases, so even with the refraction, the light hitting your eyes is coming from the road instead of the sky, thus it no longer has the bright, watery look.
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