 The angle of the incidence is the angle between the incident ray and the surface normal (an imaginary line perpendicular to the surface).Therefore, the angle of reflection is the angle between the reflected ray and the normal and a collimated beam of light does not spread out after reflection from a plane mirror, except for diffraction effects.A plane mirror makes an image of objects in front of the mirror; these images appear to be behind the plane in which the mirror lies.