Practice question

**Aerials produce radio waves** by rapid acceleration/deceleration of electrons in antenna driven by AC, frequency equals driving frequency, for 60 MHz, λ=c/f=3×10⁸/60×10⁶=5 m, half-wave antenna length λ/2=2.5 m, efficient radiation when antenna size comparable to λ. Comparing with B_y = B₀ sin(kz - ω t) , we have k = 3 × 10³ rad/m . Wavelength λ = (2 π/k) = (2 π/3 × 10³) ≈ 2.09 × 10⁻³ m . Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields 2.09 × 10⁻³ m, illustrating EM wave transverse nature and Maxwell's displacement current concept.