The University of Vermont

Physics Department

The rising sun reflects off the Atlantic ocean,

An example of specular reflection.

Light will sometimes bounce off of a surface in a phenomenon described as reflection.  When an incident beam of light strikes the surface of a smooth object, such as a mirror, the light is reflected at an angle equal to that of the angle of incident light with respect to the normal.  The normal is an imaginary line which falls perpendicular to the mirror at the point of incidence, where the light beam strikes the mirror.  The image to the right depicts the angle of incidence by the Greek letter theta with a subscript i.  Light then strikes the mirror at point O and then is reflected by an angle equal to that of the angle of incidence denoted by theta with a subscript r.  This type of reflection is referred to as specular reflection. 

A picture of diffuse reflection in a cloud on nitrogen gas.

A representation of diffuse reflection.  Drawing by GianniG46 for Wikipedia.

Drawn by Johan Arvelius for Wikipedia

Light can be reflected by an uneven surface which results in diffuse reflection as in the picture to the left.  The uneven surface causes light to reflect with many different angles which tends to scatter the beam.  This type of reflection is the kind we observe off snow or fog.