Intensity follows Malus's law for polarized light Steps:

• Incident intensity I₀ = 24 W/m², vertically polarized.
• Angle θ = 30° between vertical polarization and transmission axis.
• Apply Malus's law: I = I₀ cos²θ.
• cos(30°) = √3/2, so cos²(30°) = (3/4) = 0.75; I = 24 × 0.75 = 18 W/m².

Why A is correct:

• Malus's law gives transmitted intensity as I₀ cos²θ for polarized light, exactly 18 W/m² at θ=30°.

Why the others are wrong:

• B: 21 W/m² implies cos²θ ≈ 0.875, incorrect for 30°.
• C: 24 W/m² assumes θ=0°, full transmission.
• D: 32 W/m² exceeds incident intensity, impossible.

Final answer: A