Practice question

**Microwaves in ovens** cause water molecules to rotate at 2.45 GHz, friction heats food, penetration depth few cm, efficient heating, also radar uses reflection of microwaves from objects, Doppler shift measures speed, medical diathermy uses microwaves for tissue heating. The wave number k = (2 π/λ) . Given k = 1 rad/m , we have λ = (2 π/k) = (2 π/1) ≈ 6.28 m . Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields 6.28 m, illustrating EM wave transverse nature and Maxwell's displacement current concept.