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#polaroid

3 public questions tagged with this topic.

Optical Phenomena and Applications

What is the intensity of light after passing through two polaroids with pass-axes at \( 45^\circ \), if the initial unpo

**Incoherent sources** intensity adds I = I₁+I₂, no interference pattern because phase random, two independent sources cannot produce stable interference because phase difference fluctuates rapidly, coherent sources required with constant phase, laser coherent, visibility of fringes requires coherence, degree of coherence determines contrast. After the first polaroid, I = (I₀/2) . After the second at 45° , I = (I₀/2) cos² 45° = (I₀/2) × (1/2) = (I₀/4) . Using Δ = d sinθ, y = n λ D/d, a sinθ = n λ, I = I₀ cos²θ, n = c/v, sinC = 1/n, λ' = λ/n and A = 2a cos(φ/2), calculation gives (I₀/4),

Ref: NCERT > Physics Book > Wave Optics > Optical Phenomena and Applications

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Wavefront and Huygens Principle

Why does the intensity of transmitted light through a polaroid decrease when rotated, even if the incident light is unpo

**Wavefront types** point source spherical, distant point source plane, after convex lens plane wave focuses to point because lens adds phase delay proportional to thickness, converging spherical wavefront, after concave mirror plane wave becomes spherical converging to focus, illustrating Huygens construction. Unpolarized light becomes polarized after the first polaroid, and the second polaroid’s pass-axis alignment determines the transmitted component, reducing intensity as the angle increases. Using Δ = d sinθ, y = n λ D/d, a sinθ = n λ, I = I₀ cos²θ, n = c/v, sinC = 1/n, λ' = λ/n and A = 2

Ref: NCERT > Physics Book > Wave Optics > Wavefront and Huygens Principle

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Polarization and Malus Law

What is the intensity of light transmitted through two polaroids with their pass-axes at \( 45^\circ \) to each other, i

**Polaroid rotation** intensity varies sinusoidally with angle due to Malus law I = I₀ cos²θ, when polaroid rotated 90° from initial, intensity goes from max to zero, for unpolarized light rotating polaroid does not change intensity after first polaroid because average, but second polaroid intensity depends on relative angle, explains why intensity transmitted through two polaroids drops to zero when perpendicular. Using Malus’ law, I = I₀ cos² θ . For θ = 45° , cos 45° = (√(2)/2) , so I = I₀ ((√(2)/2))² = I₀ × (1/2) = (I₀/2) . Using Δ = d sinθ, y = n λ D/d, a sinθ =

Ref: NCERT > Physics Book > Wave Optics > Polarization and Malus Law

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