Light from the sun, depicted by yellow arrows, is scattered by small particles (black point in center) in the atmosphere (note: The sun is not visible, but is located beyond the upper left corner of this illustration). This scattered light is vertically polarized when viewed from an angle of 90º relative to the sun. The plane of polarization of the scattered light is perpendicular to the plane defined by the incident and the scattered ray. Light that is scattered at an angle of 0º is nonpolarized and at intermediate angles it is partially polarized. (After Wehner 2001.)