The magnitude of the Poynting vector of a planar electromagnetic wave has an average value of 0.724 W/m². What is the maximum value of the magnetic field in the wave? (c = 3.0 x 10⁸ m/s, μ₀ = 4π × 10^-7 T ∙ m/A, ε₀ = 8.85 × 10^-12 C²/N ∙ m²) A) 77.9 nT B) 55.1 nT C) 38.9 nT D) 108 nT E) 156 nT

Question

Quizplus · Accepted Answer

The average value of the Poynting vector S is related to the maximum magnetic field B_max by the equation S = (1/2) * c * ε_0 * E_max^2, where E_max = c * B_max. Solving for B_max gives B_max = sqrt(2 * S / (c * μ_0)). Substituting the given values, B_max = sqrt(2 * 0.724 / (3.0 x 10^8 * 4π x 10^-7)) ≈ 77.9 nT.

The Magnitude of the Poynting Vector of a Planar Electromagnetic