A plane electromagnetic wave is travelling along the X-direction. The electric field vector at an arbitrary point at a time is ⃗E=6.3 ̂j V m⁻¹. The magnetic field at that point at that time is .

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(1) 2.1×10⁻⁸ ̂k T. Given: the wave travels along +̂i, and at that point and instant ⃗E=6.3 ̂j V m⁻¹. Idea: two things are needed, the size of B from B=E/c, and its direction from the rule that ⃗E×⃗B points along the direction of travel. Size: B=(6.3)/(3×10⁸)=2.1×10⁻⁸ T. Direction: we need ̂j×̂B=̂i, and since ̂j×̂k=̂i, the magnetic field lies along +̂k. So ⃗B=2.1×10⁻⁸ ̂k T.

A plane electromagnetic wave is travelling along the X-direction. The electric field vector at an arbitrary point at a time is ⃗E=6.3 ̂j V m⁻¹. The magnetic field at that point at that time is ______.

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