As shown in figures, three identical polaroids P 1 , P 2 and P 3 are placed one after another. The pass axis of P 2 and P 3 are inclined at angle of 60 º and 90 º with respect to axis of P 1 . The source S has an intensity of 256 W m - 2 . The intensity of light at point O is _____ W m - 2 .

Step-by-step solution

As given here, the pass axis of P 2 and P 3 are inclined at angle of 60 º and 90 º with respect to axis of P 1 . Therefore, intensity of light after falling on first polaroid P 1 ,   I 1 = I 0 2 Intensity of light after falling on second polaroid P 2 ,   I 2 = I 1 cos 2 60 ° = I 0 8 Intensity of light after falling on third polaroid P 3 ,   I 3 = I 2 cos 2 30 ° = I 0 8 3 4 = 3 I 0 32 The intensity of light at O is 3 I 0 32 = 3 × 256 32 = 24   W   m - 2