Introduction

A straight stick appears bent when partially immersed in water; the sun appears oval rather than round when it is about to set; a stream may appear to be much shallower then you know it to be; the pavement shimmers on a hot summer's day.  These are some of the effects caused by the refraction of light as it passes at an angle from one medium to another.

We have already looked at refraction when we discussed water waves.  Remember what happened to the waves when they travelled obliquely between differnt depths?  The distance between the waves front changed, indicating a change in wave speed.  And because the speed of the waves changed, the direction of the waves also changed.  This was called refraction.

Now we will inquire about refraction for light waves.