91Ó°ÊÓ

Light refraction is the bending of light as it passes from one medium to another that has a different density. This change in speed causes the light to change direction. For example, light travels faster in air than in water. When it moves from air into water, it slows down and bends. This bending of light, or refraction, plays a crucial role in many everyday phenomena. One of the most fascinating examples is how we can still see the sun even after it has technically set below the horizon.

The behavior of light can be complex, but in simple terms, light travels in straight lines called rays. However, when a ray encounters a different medium, such as moving from the vacuum of space into the Earth's atmosphere, it bends. This is due to the change in speed that light experiences. The amount it bends depends on the angle at which it enters the medium and the difference in density between the two media.
In the case of a setting sun, the light rays bend as they travel through the various layers of the Earth's atmosphere, which have different densities. This bending phenomenon, called refraction, curves the path of the light rays downward, letting us see the sun just a bit longer.

The Earth's atmosphere is made up of multiple layers, each with varying densities. The lowest layer is the troposphere, where we live, followed by the stratosphere, mesosphere, and thermosphere. Each of these layers affects the behavior of light differently.
As sunlight travels through these layers, it bends due to the varying air density. This bending is known as atmospheric refraction. When the sun dips below the horizon, its light doesn't stop reaching us immediately; instead, it bends around the curve of the Earth due to the different densities in the atmosphere. This atmospheric refraction allows us to see the sun even when it has technically set below the horizon. Moments after sunset, the light we see has been bent around the Earth's curvature, creating a beautiful, lingering glow in the sky.