Practice question
Question
Why do electromagnetic waves not require a medium for propagation?
Explanation
**Poynting vector** S = E×B/μ₀ gives energy flow (W/m²), magnitude S = E B/μ₀, average = E₀ B₀/(2μ₀) = intensity, direction of propagation, showing energy transport perpendicular to E and B. Electromagnetic waves are self-sustaining oscillations of electric and magnetic fields, where a changing electric field generates a magnetic field and vice versa, requiring no material medium. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields They are self-sustaining field oscillations, illustrating EM wave transverse nature and Maxwell's displacement current concept.
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