What causes the shimmering effect on hot roads?

The shimmering effect on hot roads, often seen on summer days, is caused by the refraction of light. As the road surface heats up, it warms the air above it, creating a layer of hot, less dense air near the ground. Light passing through this layer bends, or refracts, creating the illusion of a pool of water or a shimmering surface. This effect is more pronounced on hot days when the temperature difference between the road and the air is significant.