Practice question

**Radio waves** effective for long-distance communication because low frequency waves diffract around Earth curvature and reflect from ionosphere, enabling beyond line-of-sight, used in AM (≈10⁶ Hz) ground wave, short wave sky wave. Microwaves used for satellite due to high frequency penetrates ionosphere and directional beam. All electromagnetic waves in vacuum travel at the same speed, c = 3 × 10⁸ m/s , regardless of their frequency or wavelength. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Speed, illustrating EM wave transverse nature and Maxwell's displacement current concept.