Unit 10

Light waves will potentially go on forever. Unless of course it hits a surface. In that case  it will try to reflect if possible. Specular surfaces are smooth like glass or water. If the surface imperfections are smaller than the wavelength of the incoming light waves the light will reflect nicely. But we do not live in a world with tiny imperfections, so most surfaces are what we like to call diffuse surfaces. These are more rough such as roads or fabric. Light is not as visibly reflected on these surfaces.

My disco ball has a specular surface. Actually each mirror is specular and has its own "normal." A normal is the imaginary line perpendicular to the surface. The angle of reflected light depends on the normal. According to the law of reflection the angle of incidence, or incoming light, equals the angle of reflecting light. A disco ball reflects lights in so many directions because each little mirror making it up is positioned with different "normals."