REFLECTION AND REFRACTION
Imagine a beam of light directed toward a smooth transparent surface. When it hits
this surface, some of its energy will be reflected off the surface and some will be
transmitted into the new medium. We can figure out the directions of the reflected
and transmitted beams by calculating the angles that the beams make with the
normal to the interface. The normal is a line perpendicular to the interface. In the
following figure, an incident beam strikes the boundary of another medium; it could
be a beam of light in air striking a piece of glass.