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. Using B₀ = (E₀/c) , we have B₀ = (60/3 × 10⁸) = 2 × 10⁻⁷ T . Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields 2 × 10⁻⁷ T, illustrating EM wave transverse nature and Maxwell's displacement current concept.