The magnetic field of a plane electromagnetic wave is given by B⃗ = B₀ ı̂ [cos(kz - ω t)] + B₁ ȷ̂ cos(kz + ω t) where B₀ = 3 × 10⁻⁵ T and B₁ = 2 × 10⁻⁶ T. The rms value of the force experienced by a stationary charge q = 10⁻⁴ C at z = 0 is closest to

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(4) 0.6 N. The charge is stationary, so v × B = 0 and only qE acts — the B amplitudes are only a route to E E₀₁ = cB₀ = 3 × 10⁸ × 3 × 10⁻⁵ = 9 × 10³ V m⁻¹ and E₀₂ = cB₁ = 3 × 10⁸ × 2 × 10⁻⁶ = 6 × 10² V m⁻¹ The two waves run along +z and - z with E along -ȷ̂ and -ı̂ respectively; at z = 0 both carry cos ω t, so they are perpendicular and in phase: E₀(net) = √(9000)² + (600)² = 9020 V m⁻¹ F(rms) = q E₀(net)/√2 = 10⁻⁴ × 9020/1.414 = 0.64 N ≈ 0.6 N

The magnetic field of a plane electromagnetic wave is given by B⃗ = B₀ ı̂ [cos(kz - ω t)] + B₁ ȷ̂ cos(kz + ω t) where B₀ = 3 × 10⁻⁵ T and B₁ = 2 × 10⁻⁶ T. The rms value of the force experienced by a stationary charge q = 10⁻⁴ C at z = 0 is closest to

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