refraction
Refraction The changing of a light rays direction loosely called bending when it passes through variations in matter is called refraction. Speed of Light The speed of light c not only affects refraction, it is one of the central concepts of Einsteins theory of relativity. As the accuracy of the measurements of the speed of light were improved, c was found not to depend on the velocity of the source or the observer. However, the speed of light does vary in a precise manner with the material it traverses. These facts have far-reaching implications, as we will see in Special Relativity. It makes connections between space and time and alters our expectations that all observers measure the same time for the same event, for example. The speed of light is so important that its value in a vacuum is one of the most fundamental constants in nature as well as being one of the four fundamental SI units.