What Causes Light Refraction?

causes-light-refraction Credit: Peter Roberts/CC-BY-2.0

Refraction is caused by light passing from one medium to another (from air to water, for example) and experiencing a change in speed. A fisherman looking into water to spear a fish will have to remember that refraction will distort the image he sees under the water's surface.

One of the reasons that a water-distorted image is such a good example of light refraction is not only because it is very easy to see and understand but also because air and water have a different refractive density, or optical index. This is a fancy way of saying that light waves travel at a different speed through air than they do through water, so when a light wave travels from air into water, or from water out into air, it will experience distortion because of the differences between the two media.