As shown in the figure, three identical polaroids , and are placed one after another. The pass axis of and are inclined at angle of and with respect to axis of . The source has an intensity of .
The intensity of light at point O is _______
The intensity of light at point O is _______
Show answer and solution
Answer: 24
Solution
After P₁ (polarizer), the initially unpolarized light becomes polarized with intensity I₁ = 256/2 = 128 W/m².
P₂ is at 60° to P₁, so by Malus's law: I₂ = 128 × cos²(60°) = 128 × (1/2)² = 128 × 1/4 = 32 W/m².
P₃ is at 90° to P₁, so it is at 90° - 60° = 30° to P₂: I₃ = 32 × cos²(30°) = 32 × (√3/2)² = 32 × 3/4 = 24 W/m².
P₂ is at 60° to P₁, so by Malus's law: I₂ = 128 × cos²(60°) = 128 × (1/2)² = 128 × 1/4 = 32 W/m².
P₃ is at 90° to P₁, so it is at 90° - 60° = 30° to P₂: I₃ = 32 × cos²(30°) = 32 × (√3/2)² = 32 × 3/4 = 24 W/m².
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