NEETPhysicsWave Optics
Three polaroids P₁ , P₂ , and P₃ are placed in the path of a beam of unpolarized light of intensity I₀ . The pass axes of P₁ and P₃ are crossed (at 90^ to each other). The polaroid P₂ is placed between P₁ and P₃ such that its pass axis makes an angle with that of P₁ . Match the angle in List-I with the corresponding emergent intensity from P₃ in List-II. List-I List-II (A) 15^ (I) 0 (B) 30^ (II) I₀ 32 (C) 45^ (III) 3
Options
- A(A)-(II), (B)-(III), (C)-(IV), (D)-(I)
- B(A)-(III), (B)-(II), (C)-(IV), (D)-(I)
- C(A)-(II), (B)-(IV), (C)-(III), (D)-(I)
- D(A)-(IV), (B)-(III), (C)-(II), (D)-(I)
Correct answer
A. (A)-(II), (B)-(III), (C)-(IV), (D)-(I)
Step-by-step solution
When unpolarized light of intensity I₀ passes through P₁ , the intensity becomes I₁ = I₀ 2 . The light then passes through P₂ , whose pass axis is at an angle with P₁ . By Malus's law, the intensity after P₂ is I₂ = I₁ ^2 = I₀ 2 ^2 . The pass axis of P₃ is at 90^ to P₁ , so the angle between P₂ and P₃ is (90^ - ) . The final emergent intensity from P₃ is: I₃ = I₂ ^2(90^ - ) = I₀ 2 ^2 ^2 Using (2 ) = 2 , we get I₃ = I₀ 8 ^2(2 ) . For (A) = 15^ : I₃ = I₀ 8 ^2(30^ ) = I₀ 8 1 4 = I₀ 32 . For (B) = 30^ : I₃ = I₀ 8 ^2(60