A beam of unpolarised light is incident on four polarised plates. Plates are arranged so that each plate direction is at an angle 30 ° with its previous one. What is the percentage of intensity of light coming out of final polariser-

Step-by-step solution

Intensity coming out from the first sheet, I 1 = I 0 2 Intensity coming out from the second sheet, I 2 = I 1 cos 2 30 ° = I 0 2 × 3 2 2 ⇒ I 2 = I 0 2 × 3 4 ⇒ I 2 = 3 8 I 0 Similarly, I 3 = I 2 cos 2 30 ° = 3 8 I 0 × 3 4 = 9 32 I 0 I 4 = 27 128 I 0 Now, I 4 I 0 = 27 128 ⇒ I 4 I 0 × 100 = 27 128 × 100 = 21 . 09 %