A system of three polarizers P_1, P_2, P_3 is set up such that the pass axis of P_3 is crossed with respect to that of P_1. The pass axis of P_2 is inclined at 60^o to the pass axis of P_3. When a beam of unpolarized light of intensity I_0 is incident on P_1 the intensity of light transmitted by the three polarizers is I. The ratio (I_0/I) equals (nearly):

Correct option is D. 10.67
Since unpolarised light falls on P_1 ⇒ intensity of light transmitted from P_1 = I_0/2.
Pass axis of P_3 is at an angle of 60° with P_2 ∴ Intensity of light transmitted from P_3 = (I_0/2) cos²60° = (I_0/2)(1/4) = I_0/8.
Intensity of light transmitted from P_2 = (I_0/2) cos²30° = (I_0/2)(3/4) = (3I_0)/8
Intensity of light transmitted from P_3 = (3I_0/8)cos²(60°) = (3I_0/8)(1/4) = (3I_0)/32
∴ (I_0/I) = 32/3 = 10.67