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Practice question

MCQ

Question

In electromagnetic theory, what fundamental principle allows electromagnetic waves to sustain their
propagation in vacuum without energy loss?

Options

Choose one · Correct answer highlighted

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. The principle of mutual induction, where a changing electric field induces a magnetic field and vice versa (via Faraday’s law and Ampere-Maxwell law), ensures self-sustaining propagation in vacuum without energy loss. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Mutual induction of fields, illustrating EM wave transverse nature and Maxwell's displacement current concept.

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