The vibrating E vector and the direction of propaga tion form a plane, called the plane of vibration. yue vector are in a certain constant direction E →> Y horizontal vibration Iagram:HH or-:平行振动 →1, E diagram Vertical vibration垂直振动1. Polarized light、unporarized light 偏振光、自然光 polarized light（偏振光）: the vibrations of E vector are in a certain constant direction. Z X Y u  → E  E  u  → Z X Y diagram： or diagram : horizontal vibration 平行振动 Vertical vibration 垂直振动 The vibrating E vector and the direction of propaga￾tion form a plane, called the plane of vibration.振动面