Wire grid polarizer transmits perpendicular E-field component

Steps:

• Incident microwaves are vertically polarized, with original CRO amplitude of 7.0 cm.
• Metal grid wires oriented at 20° to vertical, so angle α between wires and E-field is 20°.
• Parallel component E₀ cos 20° is blocked; transmitted component is E₀ sin 20° ≈ E₀ × 0.342.
• New CRO amplitude = 7.0 cm × 0.342 ≈ 2.4 cm (settings unchanged).

Why D is correct:

• Matches transmitted amplitude E₀ sin α per wire grid polarizer principle, where α = 20° is angle between wires and incident polarization.

Why the others are wrong:

• A: Original amplitude without polarizer effect.
• B: Incorrect; approximates 3.0 cm × sin 20° ≈ 1.0 cm, wrong base amplitude.
• C: Incorrect; approximates 3.0 cm × cos 40° ≈ 2.3 cm, misapplies angle.

Final answer: D