Practice question

**Polarization requires transverse waves** because only transverse can have orientation perpendicular to propagation, longitudinal cannot be polarized, wave theory requires light transverse to explain polarization, polaroids transmit only component along pass-axis, unpolarized has random transverse orientations, after polaroid polarized. Bright fringe position x_n = (n λ D/d) . For the fourth bright fringe, n = 4 . λ = 5.6 × 10⁻⁷ m , d = 3.5 × 10⁻⁴ m , D = 1.4 m . x₄ = (4 × 5.6 × 10⁻⁷ × 1.4/3.5 × 10⁻⁴) = 8.96 × 10⁻³ m = 8.96 mm . Using Δ = d sinθ, y = n λ