Atmospheric Optical Phenomena

One of the most familiar optical phenomena produced by refraction is a mirage. One type of mirage—the inferior mirage—is caused when a layer of air close to the ground is heated more strongly than is the air immediately above it. When that happens, light rays pass through two transparent media—the hot, less dense air and the cooler, more dense air—and are refracted. As a result of the refraction, the blue sky appears to be present on Earth's surface; it may look like a body of water and objects such as trees appear to be reflected in that water.

A second type of mirage—the superior mirage—forms when a layer of air next to the ground is much cooler than the air above it. In this situation, light rays from an object are refracted in such a way that an object appears to be suspended in air above its true position. This phenomenon is sometimes referred to as looming.