|Strange times are these in which we live, when old and young are taught in falsehoods school. And the one man that dares to tell the truth is called at once, a lunatic and fool. - Plato|
The phenomenon of refraction allows waves to be bent based on changes in the speed of the wave. The speed of sound waves shows us how sound waves are bent in air by changes in temperature.
Here we will take a look at refraction of light. The principal is exactly the same but the phenomenon is much easier to demonstrate with light.
Index of Refraction
The Index of Refraction is the ratio of the speed of light through that medium to the speed of light in a total vacuum. For example, Jean Bernard Foucault (1819 - 1868) measured the speed of light in water at about 2.26 x 108 m/s. This results in a ratio of about 1.33 when compared with the speed of light in a vacuum.
Light travels almost 2 1/2 times slower in diamonds than it does in a vacuum.
Here is a list of common mediums with their corresponding index of refraction.