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 document states that frequencies up to 54 MHz are used for short wave bands in radio communication. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Up to 54 MHz, illustrating EM wave transverse nature and Maxwell's displacement current concept.