When natural light hits a non-metallic smooth surface, such as glass, water surface, etc., the reflected light will be partially polarized after being reflected, that is, the reflected light is mixed with part of linearly polarized light and part of natural light. The proportion of linearly polarized light contained in the reflected light depends on the incident angle of the light. When the incident angle is a suitable value, the reflected light is pure linearly polarized light. This suitable angle of incidence is called polarizing angle.
