eli5: when it’s hot why does it look like there’s water on the roads and why does it make a rippling effect.
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When the sun shines on the road, the road gets hot. Way hotter than the air above it. The road will then heat up the air directly above it, but the air slightly higher up will still be a bit cooler.
When there’s a sharp surface between hot and cold air, the light rays are bent at that surface. This is the same effect that happens on a surface between glass and air (which is how lenses work), or between air and water (which is why you can see your reflection in the water) or between hot and cold water (the ripples you see when you drop an ice cube into a glass of warm water). Directly above the road, this is strong enough to reflect the light rays; the “water” you see is actually the sky reflecting. A bit higher up, it just produces the rippling where hot and cooler air mix.
It’s the same thing that is called a mirage, or a fata morgana, when it occurs in the desert.
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