What causes the shimmering effect of heat on roads?

The shimmering effect of heat on roads, called a mirage, is caused by the refraction of light. When the surface of a road becomes extremely hot, the air above it heats up and becomes less dense than the cooler air higher up. This creates a gradient in air density, causing light to bend as it passes through. The refracted light appears as if it is coming from the road’s surface, creating the illusion of water or a reflective patch. This optical phenomenon is common in hot climates.