The magnetic field of an electromagnetic wave is B⃗=1.6×10⁻⁶ cos(2×10⁷z+6×10¹⁵t)(2î+ĵ) T. Which expression gives the associated electric field?
Options

Question

The magnetic field of an electromagnetic wave is B⃗=1.6×10⁻⁶ cos(2×10⁷z+6×10¹⁵t)(2î+ĵ) T. Which expression gives the associated electric field?

G1 Physics · Accepted Answer

The phase 2×10⁷z+6×10¹⁵t represents propagation along −z. B⃗ is along 2î+ĵ. E⃗ must be perpendicular to B⃗ and satisfy E⃗×B⃗ along −z. The direction −î+2ĵ satisfies this, and |E|=c|B| gives coefficient 4.8×10² V m⁻¹. Option D.