3. The law of Malus: Intensity I of the polarized light( intensity lo) transmitted polarizing sheet varies I=l0cos2a。 (a is the angle between the polarizing directions of the sheet and vibration direction of polarized light I=locos E 例:一束自然光,光强度为I,让其出射两个偏振 片,两个偏振片之间的夹角为45,求从第二 个偏振片出射的偏振光强度。3. The law of Malus: Intensity I of the polarized light ( intensity I0 ) transmitted polarizing sheet varies: I=I0 cos2。 ( is the angle between the polarizing directions of the sheet and vibration direction of polarized light） E⊥ E// E0   I=I0 cos2 例：一束自然光，光强度为I0，让其出射两个偏振 片，两个偏振片之间的夹角为450，求从第二 个偏振片出射的偏振光强度。 I0