What Are Reflection and Refraction?

Reflection and refraction are two of the ways light interacts with matter, with absorption being the third. Reflection occurs when incoming light is bounced off of a surface. Reflection can be either coherent, as it is with a mirror, or incoherent as when light reflects off of a white surface. Refraction entails the slowing and bending of light as it moves through a medium.

The degree to which a surface reflects light is a measurable quality called albedo. The higher the albedo, the more incoming light the surface is able to reflect. Surfaces with low albedo usually absorb incoming light rather than reflect or refract it.

Refraction occurs as light transitions from one medium, such as air, to another such as glass or water. As they pass through the transparent substance, waves of light slow down or speed up depending on the density of the new medium. The various wavelengths of white light each slow at a different rate, which bends some wavelengths more than others. The result of this is that light passing through droplets of water suspended in a cloud or a glass prism in a laboratory can spread out into its constituent colors and form a rainbow.